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.

docs/features/magic-notes/progress.md

@@ -1,5 +1,30 @@
 # Magic Notes Progress
 
+## 2026-09-28: Startup Body Read Reuse
+
+Startup repair now reuses the asset references collected during revision
+inspection, as described in [file reconciliation](./technical-design.md#schema-38-migration).
+The persisted format and revision recovery rules are unchanged.
+
+- Real temporary SQLite/filesystem fixture: 120 entries across 120 notes,
+  half rich text and half canvas, with 4,039,560 bytes of body JSON.
+  Five initializations each read 240 bodies before and 120 after the change.
+  Logical bytes read fell from 8,079,120 to 4,039,560 per initialization.
+- Baseline durations were 148.23, 134.42, 131.06, 140.66 and 172.90 ms;
+  after durations were 136.89, 119.11, 116.41, 115.14 and 116.26 ms.
+  Medians were 140.66 and 116.41 ms. These Windows runs used warm filesystem
+  caches on a shared machine; they do not measure cold application startup.
+- `npx vitest run src/main/magic-notes/magic-note-storage.test.ts src/main/assistant/assistant-database.test.ts src/main/assistant/assistant-storage-upgrade.test.ts src/main/assistant-storage-startup.test.ts tests/assistant-storage-worker.test.ts`
+  passed 154 tests. Coverage includes failed media inspection, missing/invalid
+  bodies, retained shared assets, revision mismatch recovery and migration.
+- Full `npm test`: 5382 passed, 84 skipped, 3 failed. The failures were the
+  App question-round request wait and Electron note capture focus/layout waits.
+  All three passed in targeted reruns; the full run was not all green.
+  The capture rerun exercised production App/preload/IPC/SQLite and reopening.
+- `npm run typecheck` passed. Full lint still reports 10 errors in the existing
+  untracked `sidebar-final-probe.ts` and `sidebar-final-run.mjs`; lint excluding
+  those two files passed. No provider calls were made for these storage benchmarks.
+
 ## 2026-09-27: Shared Destructive Button Styles
 
 The draft discard Portal now receives the global `danger-solid` styles. The

docs/features/magic-notes/technical-design.md

@@ -173,7 +173,12 @@ empty content. Failed creates leave no accepted database membership; their
 unaccepted files are removed on the next access or reopen.
 
 After commit, reconciliation derives `note.json` from database membership and
-scans all retained entry files before removing unreferenced assets. Manifest or
+inspects all retained entry files before removing unreferenced assets. Startup
+repair reads each current body once to inspect its revision and collect asset
+references, then passes the complete per-note reference set to reconciliation.
+If media inspection fails, cleanup uses its existing deferred retry path rather
+than trusting a partial set. Revision mismatch recovery still hydrates the body;
+legacy conversion still verifies its written content. Manifest or
 GC failures log `console.warn` with the note ID and error and remain in an
 in-memory retry set. Later database access retries; reopening derives cleanup
 again from membership. These cleanup failures do not turn a committed save,