feat(editor): add revision/status/tracking_number FM hints + filename-mismatch warning

Per review: the doctype templates render $revision$, $status$, $tracking_number$
and $title$, so they belong in the recognised front-matter list — added them
(alongside the existing title) to convert.RecognizedFrontMatter.

These four are the document's canonical identity, sourced from the ZDDC
filename. Policy (chosen): the filename WINS — the rendered doc always uses the
filename-derived value (the HTML/PDF templates read it from the filename-derived
pandoc -V flags, which override YAML metadata). Front matter must not silently
diverge, so:
  - their hints now read "set by the filename (the filename wins on mismatch)";
  - the markdown editor shows a non-blocking warning when front matter sets one
    of the four to a value differing from the filename (gated on a conventional
    ZDDC filename — non-conventional files have no canonical identity, so front
    matter stays free there).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

browse/js/preview-markdown.js

@@ -411,7 +411,18 @@
         fmTextarea.placeholder = '';
         applyFrontMatterPlaceholder(fmTextarea);
         fmBody.appendChild(fmTextarea);
+        // Non-blocking warning shown when front matter disagrees with the
+        // canonical filename on an identity field (tracking_number / revision /
+        // status / title). The filename always wins in the rendered doc; this
+        // just tells the author their front-matter value is being ignored.
+        var fmWarn = document.createElement('div');
+        fmWarn.className = 'md-fm__warn';
+        fmWarn.hidden = true;
+        fmWarn.style.cssText = 'color:#92400e;background:#fffbeb;border:1px solid '
+            + '#fcd34d;border-radius:4px;padding:4px 8px;margin:0 0 4px;font-size:'
+            + '0.78rem;line-height:1.4;';
         fmSection.appendChild(fmHeader);
+        fmSection.appendChild(fmWarn);
         fmSection.appendChild(fmBody);
         sidebar.appendChild(fmSection);
 
@@ -736,14 +747,49 @@
         }, 250);
         editor.on('change', onChange);
 
+        // Identity fields are sourced from the canonical ZDDC filename; setting
+        // a different value in front matter is ignored at render (the filename
+        // wins). Surface a mismatch so the author isn't silently overridden.
+        // Maps the front-matter key to the parseFilename field.
+        var IDENTITY_FIELDS = [
+            { fm: 'title', fn: 'title', label: 'title' },
+            { fm: 'tracking_number', fn: 'trackingNumber', label: 'tracking number' },
+            { fm: 'revision', fn: 'revision', label: 'revision' },
+            { fm: 'status', fn: 'status', label: 'status' }
+        ];
+        function checkFilenameMismatch() {
+            var z = window.zddc;
+            var fn = (z && z.parseFilename) ? z.parseFilename(node.name) : null;
+            // Only meaningful for a conventional ZDDC filename (it always has a
+            // tracking number). Non-conventional files have no canonical
+            // identity, so front matter is free — no warning.
+            if (!fn || !fn.trackingNumber) { fmWarn.hidden = true; return; }
+            var data = parseFrontMatter('---\n' + fmTextarea.value + '\n---\n').data || {};
+            var clashes = [];
+            IDENTITY_FIELDS.forEach(function (f) {
+                if (!(f.fm in data)) return;
+                var got = String(data[f.fm] == null ? '' : data[f.fm]).trim();
+                var want = String(fn[f.fn] == null ? '' : fn[f.fn]).trim();
+                if (got !== '' && want !== '' && got !== want) {
+                    clashes.push(f.label + ' “' + got + '” ≠ filename “' + want + '”');
+                }
+            });
+            if (!clashes.length) { fmWarn.hidden = true; fmWarn.textContent = ''; return; }
+            fmWarn.textContent = '⚠ Front matter disagrees with the filename (the '
+                + 'filename wins): ' + clashes.join('; ') + '.';
+            fmWarn.hidden = false;
+        }
+
         var onFmChange = debounce(async function () {
             if (currentInstance !== instance) return;
             var body = editor.getMarkdown();
             var h = await hashContent(assembleContent(fmTextarea.value, body));
             if (currentInstance !== instance) return;
             markDirty(h !== instance.hash);
+            checkFilenameMismatch();
         }, 250);
         fmTextarea.addEventListener('input', onFmChange);
+        checkFilenameMismatch(); // initial state on load
 
         // ── Save ───────────────────────────────────────────────────────────
         // Mark a successful write: adopt the new server ETag (so the next

zddc/internal/convert/convert.go

@@ -78,7 +78,10 @@ func RecognizedFrontMatter() []FrontMatterField {
 	return []FrontMatterField{
 		{"doctype", "report | letter | specification"},
 		{"numbering", "true to number headings (default false)"},
-		{"title", "overrides the filename-derived title"},
+		{"title", "set by the filename (the filename wins on mismatch)"},
+		{"tracking_number", "set by the filename (the filename wins on mismatch)"},
+		{"revision", "set by the filename (the filename wins on mismatch)"},
+		{"status", "set by the filename (the filename wins on mismatch)"},
 		{"date", "document date (free text)"},
 		{"custom_header", "extra line shown in the document header"},
 		{"client", "overrides the .zddc convert: cascade"},

zddc/internal/handler/converthandler_test.go

@@ -90,8 +90,9 @@ func TestServeFrontMatterTemplate(t *testing.T) {
 	if len(payload.Fields) == 0 {
 		t.Fatal("fields empty")
 	}
-	// The two keys with no other source are the ones authors most need hinted.
+	// doctype/numbering have no other source; revision/status are template
-	for _, want := range []string{"doctype", "numbering"} {
+	// fields an author can override here — all must be communicated.
+	for _, want := range []string{"doctype", "numbering", "revision", "status", "tracking_number"} {
 		if !strings.Contains(payload.Placeholder, want) {
 			t.Errorf("placeholder missing %q: %q", want, payload.Placeholder)
 		}