feat(phase9): frontend types + persistence wiring for llmTags

TranscriptEntry gains llmTags: string[]; TranscriptRow gains the
storage-shape llmTags: string. ContentTags type added. mapTranscriptRow
hydrates llmTags from the comma-joined column. saveTranscriptMeta
forwards llmTags through to update_transcript_meta_cmd, mirroring the
existing manualTags handling.

buildFrontmatter unions auto + manual + llm tags so exported markdown
surfaces every source in one tags: list.

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

src/lib/stores/page.svelte.ts

@@ -144,6 +144,8 @@ function mapTranscriptRow(row: TranscriptDto): TranscriptEntry {
   const text = row.text ?? "";
   const rawTags = row.manualTags ?? "";
   const manualTags = rawTags ? rawTags.split(",").filter(Boolean) : [];
+  const rawLlmTags = row.llmTags ?? "";
+  const llmTags = rawLlmTags ? rawLlmTags.split(",").filter(Boolean) : [];
   const rawSegments = row.segmentsJson ?? "";
   let segments: Segment[] = [];
   if (rawSegments) {
@@ -173,6 +175,7 @@ function mapTranscriptRow(row: TranscriptDto): TranscriptEntry {
     template: row.template ?? "",
     language: row.language ?? "",
     segments,
+    llmTags,
   };
 }
 
@@ -196,6 +199,7 @@ function normaliseTranscriptEntry(entry: TranscriptWriteEntry): TranscriptEntry
     template: entry.template ?? "",
     language: entry.language ?? "",
     segments: Array.isArray(entry.segments) ? entry.segments : [],
+    llmTags: Array.isArray(entry.llmTags) ? entry.llmTags : [],
   };
 }
 
@@ -292,6 +296,11 @@ export async function saveTranscriptMeta(id: string, patch: TranscriptMetaPatch)
       template: patch.template,
       language: patch.language,
       segmentsJson: patch.segments === undefined ? undefined : JSON.stringify(patch.segments),
+      llmTags: patch.llmTags == null
+        ? undefined
+        : (Array.isArray(patch.llmTags)
+            ? patch.llmTags.join(",")
+            : String(patch.llmTags)),
     };
     const row = await invoke<TranscriptDto>("update_transcript_meta_cmd", {
       id: String(id),