fix: reduce redundant work during chat and note startup

Avoid hidden activity renders, no-op message saves and attachment scans when pinning conversations. Reuse note body inspection and skip unchanged attachment reference writes while preserving recovery and cleanup behavior.

Skip unnecessary Markdown normalization and memoize subagent lookups without delaying live rich text. Add storage operation counts and real Electron rendering equivalence benchmarks; full-render speedup remains unproven.

Validation: 5397 tests passed, 84 skipped; typecheck passed. Lint passed excluding two existing untracked sidebar probe files.

Release note: Reduce repeated rendering and disk work during chat, conversation pinning and note startup while preserving existing content and interactions.

src/main/assistant/assistant-database.ts

@@ -1888,7 +1888,7 @@ export class AssistantDatabase {
     return JSON.stringify({ storage: 'file', version: content.version, revision })
   }
 
-  private reconcileMagicNoteFiles(noteId?: string): void {
+  private reconcileMagicNoteFiles(noteId?: string, inspectedAssets?: ReadonlySet<string>): void {
     const database = this.database!
     // SQL and authoritative bodies are already committed. Cleanup must never
     // turn an accepted save/delete/reset into a retryable UI write failure.
@@ -1901,7 +1901,7 @@ export class AssistantDatabase {
         else this.noteStorage.clear()
       } else if (database.prepare('SELECT id FROM magic_notes WHERE id = ?').get(noteId)) {
         const entries = database.prepare('SELECT id FROM magic_note_entries WHERE note_id = ? ORDER BY created_at, rowid').all(noteId) as Array<{ id: string }>
-        this.noteStorage.reconcile(noteId, entries.map((entry) => entry.id))
+        this.noteStorage.reconcile(noteId, entries.map((entry) => entry.id), inspectedAssets)
       } else {
         this.noteStorage.deleteNote(noteId)
       }
@@ -1929,6 +1929,7 @@ export class AssistantDatabase {
     let processed = 0
     let migrated = false
     for (const note of notes) {
+      let referencedAssets: Set<string> | undefined = new Set<string>()
       const entries = database.prepare('SELECT id FROM magic_note_entries WHERE note_id = ? ORDER BY created_at, rowid').all(note.id) as Array<{ id: string }>
       for (const { id } of entries) {
         if (isCancelled()) throw new DOMException('Upgrade cancelled', 'AbortError')
@@ -1937,6 +1938,7 @@ export class AssistantDatabase {
           // One payload at a time: a canvas may contain a large PDF.
           const row = database.prepare('SELECT * FROM magic_note_entries WHERE id = ?').get(id) as MagicNoteEntryRow
           const pointer = JSON.parse(row.content_json) as { storage?: string; revision?: number }
+          const inspected = pointer.storage === 'file' ? this.noteStorage.inspect(note.id, id) : undefined
           if (pointer.storage !== 'file') {
             const content = JSON.parse(row.content_json) as MagicNoteContent
             this.noteStorage.write({ noteId: note.id, id, content, revision: row.revision, updatedAt: row.updated_at })
@@ -1948,7 +1950,7 @@ export class AssistantDatabase {
               magicNotePlainText(content), magicNoteEmbeddedBytes(content), id
             )
             migrated = true
-          } else if (this.noteStorage.revision(note.id, id) !== pointer.revision) {
+          } else if (inspected!.revision !== pointer.revision) {
             const saved = this.noteStorage.read(note.id, id)
             database.prepare(`UPDATE magic_note_entries SET content_json = ?, plain_text = ?, image_bytes = ?,
               revision = MAX(revision, ?), updated_at = ?, comments_json = '[]', analyzed_at = NULL WHERE id = ?`).run(
@@ -1958,6 +1960,9 @@ export class AssistantDatabase {
             database.prepare('UPDATE magic_notes SET revision = revision + 1, updated_at = ? WHERE id = ?').run(saved.updatedAt, note.id)
             this.syncMagicNoteTodos(database, note.id, id, saved.content, saved.updatedAt)
           }
+          const assets = (inspected ?? this.noteStorage.inspect(note.id, id)).referencedAssets
+          if (!assets) referencedAssets = undefined
+          else if (referencedAssets) for (const asset of assets) referencedAssets.add(asset)
           database.exec('COMMIT')
         } catch (error) {
           database.exec('ROLLBACK')
@@ -1966,7 +1971,7 @@ export class AssistantDatabase {
         processed++
         if (migrated) onProgress?.({ stage: 'converting', processed, total, bytesBefore })
       }
-      this.reconcileMagicNoteFiles(note.id)
+      this.reconcileMagicNoteFiles(note.id, referencedAssets)
     }
     if (!noteIds) this.reconcileMagicNoteFiles()
     this.dirtyMagicNotes.clear()