refactor(archive): use shared zddc.ParseTransmittalFolder

The transmittal-folder grammar was duplicated as a private regex inside
the archive package. Replace the local regex with calls to the shared
parser in zddc/internal/zddc/folder.go so the grammar lives in one
place and the upcoming staging→working mirror logic can reuse it.

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

zddc/internal/archive/index.go

@@ -9,6 +9,8 @@ import (
 	"strings"
 	"sync"
 	"time"
+
+	"codeberg.org/VARASYS/ZDDC/zddc/internal/zddc"
 )
 
 // RevisionEntry holds the resolved file paths for one base revision.
@@ -49,9 +51,6 @@ func NewIndex() *Index {
 	}
 }
 
-// transmittalFolderRE matches: YYYY-MM-DD_anything (anything) - anything
-var transmittalFolderRE = regexp.MustCompile(`^(\d{4}-\d{2}-\d{2})_[^_\s]+\s*\([^)]+\)\s*-\s*.+$`)
-
 // zddc filename: trackingNumber_revision (status) - title.ext
 // trackingNumber: no spaces or underscores
 // revision: ~?[A-Z0-9]+(+[CBNQ][0-9]+)?
@@ -101,9 +100,8 @@ func walkAndIndex(idx *Index, fsRoot, dirAbs, serverDir string) error {
 		}
 		childAbs := filepath.Join(dirAbs, name)
 
-		if m := transmittalFolderRE.FindStringSubmatch(name); m != nil {
+		if date, _, _, _, ok := zddc.ParseTransmittalFolder(name); ok {
 			// This is a transmittal folder — index its files
-			date := m[1]
 			if err := indexTransmittalFolder(idx, fsRoot, childAbs, childServerDir, date); err != nil {
 				// Non-fatal: log and continue
 				continue
@@ -340,11 +338,10 @@ func (idx *Index) Rebuild(fsRoot string) (time.Duration, int, int, error) {
 func (idx *Index) UpdateFromDir(fsRoot, transmittalDirPath string) error {
 	// Determine the date from the folder name
 	folderName := filepath.Base(transmittalDirPath)
-	m := transmittalFolderRE.FindStringSubmatch(folderName)
-	if m == nil {
+	date, _, _, _, ok := zddc.ParseTransmittalFolder(folderName)
+	if !ok {
 		return nil // not a transmittal folder
 	}
-	date := m[1]
 
 	// Compute server-relative path for this folder
 	rel, err := filepath.Rel(fsRoot, transmittalDirPath)

zddc/internal/archive/watcher.go

@@ -109,7 +109,7 @@ func (w *Watcher) handleEvent(event fsnotify.Event) {
 	// For transmittal folder events, schedule a debounced index update
 	dirPath := filepath.Dir(path)
 	dirName := filepath.Base(dirPath)
-	if transmittalFolderRE.MatchString(dirName) {
+	if _, _, _, _, ok := zddc.ParseTransmittalFolder(dirName); ok {
 		w.scheduleIndexUpdate(dirPath)
 	}
 }