feat(dispatch): trailing slash → browse, no slash → canonical default tool

URL convention for directories under a project:

- <dir>/  (with trailing slash)  → browse (the directory view; same
                                     behaviour as today)
- <dir>   (without trailing slash) → the canonical default tool for
                                     that directory's context, served
                                     inline (no 301 hop)

Tool mapping via the new apps.DefaultAppAt(root, dir):

  - working/...               → mdedit
  - staging/...               → transmittal
  - archive/                  → archive
  - archive/<party>/          → archive
  - archive/<party>/incoming|received|issued/...  → archive
  - archive/<party>/mdl/...   → tables (the per-party MDL grid editor)

Directories outside the canonical layout (project root, scratch
folders) keep the legacy 301-to-trailing-slash redirect since no
default tool fits.

This generalises and replaces the bespoke
"GET archive/<party>/mdl/ → 302 mdl.table.html" redirect added in PR4.
The new dispatcher rule serves the table app inline at the bare-mdl
URL by routing through RecognizeTableRequest with the canonical
.table.html suffix appended; relative fetches resolve identically
because both URLs share the same parent directory.

Tests: TestDefaultAppAt covers all canonical positions plus
case-fold and out-of-tree edges. TestDispatchSlashRouting (replacing
the now-obsolete TestDispatchMdlRedirect) verifies the slash-vs-no-
slash distinction at every canonical folder + non-canonical
fallback.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

zddc/cmd/zddc-server/main.go

@@ -529,23 +529,6 @@ func dispatch(cfg config.Config, idx *archive.Index, ring *handler.LogRing, apps
 		return
 	}
 
-	// MDL convenience redirect: GET archive/<party>/mdl/ → mdl.table.html.
-	// The table app is the canonical view for the per-party Master
-	// Deliverables List. Direct navigation to the data folder lands on
-	// the grid editor; clients that want the raw row listing can still
-	// hit archive/<party>/mdl/ via the file API or with an explicit
-	// trailing-segment beyond mdl/.
-	if (r.Method == http.MethodGet || r.Method == http.MethodHead) && len(segments) == 4 {
-		if strings.EqualFold(segments[1], "archive") && strings.EqualFold(segments[3], "mdl") {
-			target := "/" + segments[0] + "/" + segments[1] + "/" + segments[2] + "/mdl.table.html"
-			if r.URL.RawQuery != "" {
-				target += "?" + r.URL.RawQuery
-			}
-			http.Redirect(w, r, target, http.StatusFound)
-			return
-		}
-	}
-
 	// Tables-system intercept: *.table.html is a virtual URL that the
 	// table handler renders inline, reading rows from a directory of
 	// *.yaml files declared in the directory's .zddc tables: map.
@@ -680,6 +663,37 @@ func dispatch(cfg config.Config, idx *archive.Index, ring *handler.LogRing, apps
 				return
 			}
 		}
+		// URL convention: trailing slash → browse (handled by
+		// ServeDirectory, which serves browse.html for HTML requests
+		// and JSON for application/json). No trailing slash → the
+		// canonical default tool for this directory's context, if any
+		// (mdedit under working/, transmittal under staging/, archive
+		// under archive/, tables under archive/<party>/mdl/). When no
+		// default applies, fall back to the historical redirect-to-
+		// trailing-slash behaviour.
+		if !strings.HasSuffix(urlPath, "/") && (r.Method == http.MethodGet || r.Method == http.MethodHead) && !isRoot {
+			switch apps.DefaultAppAt(cfg.Root, absPath) {
+			case "tables":
+				// Tables aren't an apps-subsystem app — the table
+				// handler responds to <dir>/<name>.table.html. Serve
+				// the equivalent table view inline at the bare-mdl
+				// URL by routing through the handler with the
+				// canonical .table.html name appended.
+				if tr := handler.RecognizeTableRequest(cfg.Root, http.MethodGet, urlPath+".table.html"); tr != nil {
+					handler.ServeTable(cfg, tr, w, r)
+					return
+				}
+			case "archive", "transmittal", "mdedit":
+				if appsSrv != nil {
+					app := apps.DefaultAppAt(cfg.Root, absPath)
+					if apps.AppAvailableAt(cfg.Root, absPath, app) {
+						chain, _ := zddc.EffectivePolicy(cfg.Root, absPath)
+						appsSrv.Serve(w, r, app, chain, absPath)
+						return
+					}
+				}
+			}
+		}
 		if !strings.HasSuffix(urlPath, "/") {
 			http.Redirect(w, r, urlPath+"/", http.StatusMovedPermanently)
 			return

zddc/cmd/zddc-server/main_test.go

@@ -373,11 +373,26 @@ func TestDispatchArchiveRedirect(t *testing.T) {
 	}
 }
 
-func TestDispatchMdlRedirect(t *testing.T) {
+func TestDispatchSlashRouting(t *testing.T) {
+	// Convention: <dir>/ → browse (directory view); <dir> → the canonical
+	// default tool for the directory (mdedit under working/, transmittal
+	// under staging/, archive under archive/, tables under
+	// archive/<party>/mdl/). Without a default app, no-slash falls
+	// through to the legacy 301-to-trailing-slash redirect.
 	root := t.TempDir()
 	mustWrite(t, filepath.Join(root, ".zddc"),
-		"acl:\n  permissions:\n    \"*@example.com\": rwcda\n")
+		"acl:\n  permissions:\n    \"*\": rwcda\n")
-	mustMkdir(t, filepath.Join(root, "ProjectA", "archive", "Acme"))
+	for _, sub := range []string{
+		"Project/working",
+		"Project/staging",
+		"Project/archive",
+		"Project/archive/Acme",
+		"Project/archive/Acme/incoming",
+		"Project/archive/Acme/mdl",
+		"Project/scratch",
+	} {
+		mustMkdir(t, filepath.Join(root, sub))
+	}
 
 	idx, err := archive.BuildIndex(root)
 	if err != nil {
@@ -389,58 +404,46 @@ func TestDispatchMdlRedirect(t *testing.T) {
 		EmailHeader: "X-Auth-Request-Email",
 	}
 	ring := handler.NewLogRing(10)
+	appsSrv, err := setupApps(cfg)
+	if err != nil {
+		t.Fatalf("setupApps: %v", err)
+	}
 
 	cases := []struct {
 		name           string
 		path           string
 		wantStatus     int
-		wantLoc    string
+		wantNoRedirect bool
 	}{
-		{
+		{"working no-slash → mdedit", "/Project/working", http.StatusOK, true},
-			"mdl trailing slash → table",
+		{"working slash → browse", "/Project/working/", http.StatusOK, true},
-			"/ProjectA/archive/Acme/mdl/",
+		{"staging no-slash → transmittal", "/Project/staging", http.StatusOK, true},
-			http.StatusFound,
+		{"staging slash → browse", "/Project/staging/", http.StatusOK, true},
-			"/ProjectA/archive/Acme/mdl.table.html",
+		{"archive no-slash → archive", "/Project/archive", http.StatusOK, true},
-		},
+		{"archive slash → browse", "/Project/archive/", http.StatusOK, true},
-		{
+		{"archive/<party> no-slash → archive", "/Project/archive/Acme", http.StatusOK, true},
-			"case-fold MDL trailing slash",
+		{"archive/<party> slash → browse", "/Project/archive/Acme/", http.StatusOK, true},
-			"/ProjectA/archive/Acme/MDL/",
+		{"archive/<party>/mdl no-slash → tables", "/Project/archive/Acme/mdl", http.StatusOK, true},
-			http.StatusFound,
+		{"archive/<party>/mdl slash → browse", "/Project/archive/Acme/mdl/", http.StatusOK, true},
-			"/ProjectA/archive/Acme/mdl.table.html",
+		{"archive/<party>/incoming no-slash → archive", "/Project/archive/Acme/incoming", http.StatusOK, true},
-		},
+		{"archive/<party>/incoming slash → browse", "/Project/archive/Acme/incoming/", http.StatusOK, true},
-		{
+		{"non-canonical no-slash → 301 to slash", "/Project/scratch", http.StatusMovedPermanently, false},
-			"case-fold ARCHIVE",
+		{"non-canonical slash → browse", "/Project/scratch/", http.StatusOK, true},
-			"/ProjectA/Archive/Acme/mdl/",
+		{"project root no-slash → 301 to slash", "/Project", http.StatusMovedPermanently, false},
-			http.StatusFound,
-			"/ProjectA/Archive/Acme/mdl.table.html",
-		},
-		{
-			"deeper than party-level mdl is NOT redirected",
-			"/ProjectA/archive/Acme/incoming/mdl/",
-			// Falls through to static-file pipeline; no folder exists there → 404.
-			http.StatusNotFound,
-			"",
-		},
-		{
-			"working/mdl is NOT redirected (not under archive)",
-			"/ProjectA/working/mdl/",
-			http.StatusNotFound,
-			"",
-		},
 	}
 
 	for _, tc := range cases {
 		t.Run(tc.name, func(t *testing.T) {
 			req := httptest.NewRequest(http.MethodGet, tc.path, nil)
 			rec := httptest.NewRecorder()
-			dispatch(cfg, idx, ring, nil, rec, req)
+			dispatch(cfg, idx, ring, appsSrv, rec, req)
 			if rec.Code != tc.wantStatus {
-				t.Fatalf("path=%q status=%d, want %d; body=%s", tc.path, rec.Code, tc.wantStatus, rec.Body.String())
+				t.Fatalf("path=%q status=%d, want %d; body=%s",
-			}
+					tc.path, rec.Code, tc.wantStatus, rec.Body.String())
-			if tc.wantLoc != "" {
-				if got := rec.Header().Get("Location"); got != tc.wantLoc {
-					t.Errorf("path=%q Location=%q, want %q", tc.path, got, tc.wantLoc)
 			}
+			if tc.wantNoRedirect && rec.Code >= 300 && rec.Code < 400 {
+				t.Errorf("path=%q unexpected redirect to %q",
+					tc.path, rec.Header().Get("Location"))
 			}
 		})
 	}

zddc/internal/apps/availability.go

@@ -68,3 +68,56 @@ func inAncestorWithName(root, requestDir string, names ...string) bool {
 	}
 	return false
 }
+
+// DefaultAppAt returns the canonical default tool name for requestDir,
+// or "" if no specific tool fits. Used by the dispatcher to decide
+// which app to serve at a directory URL with no trailing slash —
+// trailing-slash URLs serve the browse app for any directory.
+//
+// Rules (case-insensitive on canonical folder names):
+//
+//   - <project>/archive/<party>/mdl/...    → "tables"
+//   - <project>/archive/                   → "archive"
+//   - <project>/archive/<party>/...        → "archive"
+//   - <project>/staging/...                → "transmittal"
+//   - <project>/working/...                → "mdedit"
+//   - any other directory                  → "" (no default)
+//
+// The mdl rule wins over the broader archive rule because the table
+// editor is a more specific surface for browsing planned deliverables
+// than the archive index.
+//
+// requestDir and root are absolute filesystem paths; requestDir must
+// be under root (otherwise "" is returned).
+func DefaultAppAt(root, requestDir string) string {
+	root = filepath.Clean(root)
+	requestDir = filepath.Clean(requestDir)
+	if requestDir == root {
+		return ""
+	}
+	rel, err := filepath.Rel(root, requestDir)
+	if err != nil || strings.HasPrefix(rel, "..") {
+		return ""
+	}
+	parts := strings.Split(rel, string(filepath.Separator))
+	if len(parts) < 2 {
+		// Project root itself — no default tool.
+		return ""
+	}
+	// The project segment is parts[0]; canonical folder is parts[1].
+	canonical := strings.ToLower(parts[1])
+	switch canonical {
+	case "archive":
+		// Inside archive/. Check for the mdl sub-case at depth 4
+		// (parts: project, archive, party, mdl).
+		if len(parts) >= 4 && strings.EqualFold(parts[3], "mdl") {
+			return "tables"
+		}
+		return "archive"
+	case "staging":
+		return "transmittal"
+	case "working":
+		return "mdedit"
+	}
+	return ""
+}

zddc/internal/apps/availability_test.go

@@ -67,3 +67,49 @@ func TestAppAvailableAt(t *testing.T) {
 		})
 	}
 }
+
+func TestDefaultAppAt(t *testing.T) {
+	root := "/srv/zddc"
+	cases := []struct {
+		dir  string
+		want string
+	}{
+		// At the deployment root itself, no default tool — landing handles
+		// the project picker via a separate path.
+		{root, ""},
+		// Bare project root: no default. Trailing-slash URL serves browse;
+		// no-slash falls through to the redirect.
+		{root + "/Project-A", ""},
+		// Canonical project-root folders.
+		{root + "/Project-A/working", "mdedit"},
+		{root + "/Project-A/working/alice@example.com", "mdedit"},
+		{root + "/Project-A/working/2026-06-15_x (DFT) - y", "mdedit"},
+		{root + "/Project-A/staging", "transmittal"},
+		{root + "/Project-A/staging/2026-06-15_x (DFT) - y", "transmittal"},
+		// archive: at the archive root, party folders, and per-party
+		// subfolders (incoming/received/issued).
+		{root + "/Project-A/archive", "archive"},
+		{root + "/Project-A/archive/Acme", "archive"},
+		{root + "/Project-A/archive/Acme/incoming", "archive"},
+		{root + "/Project-A/archive/Acme/issued", "archive"},
+		{root + "/Project-A/archive/Acme/received", "archive"},
+		// mdl wins over the broader archive rule.
+		{root + "/Project-A/archive/Acme/mdl", "tables"},
+		{root + "/Project-A/archive/Acme/mdl/anything-deeper", "tables"},
+		// reviewing/ is virtual — no default tool wired here yet.
+		{root + "/Project-A/reviewing", ""},
+		// Random non-canonical folder names → no default.
+		{root + "/Project-A/scratch", ""},
+		// Case-fold on canonical names.
+		{root + "/Project-A/Working", "mdedit"},
+		{root + "/Project-A/STAGING", "transmittal"},
+		{root + "/Project-A/Archive/Acme/MDL", "tables"},
+	}
+	for _, tc := range cases {
+		t.Run(tc.dir, func(t *testing.T) {
+			if got := DefaultAppAt(root, tc.dir); got != tc.want {
+				t.Errorf("DefaultAppAt(%q) = %q, want %q", tc.dir, got, tc.want)
+			}
+		})
+	}
+}