feat(sync): F3 — drop updatedAt as a synced data field

Removes `updatedAt` from the wire protocol and from every Local-prefixed
record type. Replaced by two orthogonal mechanisms — deriveUpdatedAt()
for read-side public-facing values, _updatedAtIndex shadow for indexed
sorts.

Local-side:
- New `_updatedAtIndex` shadow column. Stamped by the Dexie creating /
  updating hook on every write. Stripped from the pending-change payload
  so it never travels to mana-sync. Indexed in Dexie v53 on the 22 tables
  that previously indexed `updatedAt`.
- `deriveUpdatedAt(record)` in sync.ts returns max(__fieldMeta[*].at) so
  the public-facing Task / Note / etc. shape keeps an `updatedAt: string`
  property without holding it as data.
- Type-converters across ~60 module/queries.ts and types.ts files now
  call `deriveUpdatedAt(local)` instead of reading `local.updatedAt`.

Module-store sweep:
- Regex codemod removed `updatedAt: new Date().toISOString()` /
  `: now` / `: now()` / `: nowIso()` stamping from 121 store files
  (~382 call sites total). Single-property update calls
  (`{ updatedAt: now }`) collapsed to `{}`; touch-only patterns
  (writing/drafts, writing/generations) kept the call as a no-op
  because the hook now stamps `_updatedAtIndex` automatically on
  any Dexie modification.
- Local* interfaces stripped of `updatedAt: string` (43 types.ts files).
  Public-facing types (Task, Note, Mission, Agent, …) keep
  `updatedAt: string` as a computed read-side property.
- Companion's chat conversation now sorts on a real
  `lastMessageAt` data field instead of touching `updatedAt`.
- Session-only stores (times/session-alarms, session-countdown-timers)
  stamp `updatedAt: now` directly because they're not in Dexie and
  have no field-meta layer to derive from.

Sync engine:
- applyServerChanges sets `_updatedAtIndex` itself when applying
  server changes (max of server-field times for updates, recordTime
  for inserts) so server-replays land orderable.
- Dropped the legacy `localUpdatedAt` fallback — every record now has
  `__fieldMeta`, the per-field at is the canonical source.
- Soft-delete tombstone path stops stamping `updatedAt: serverTime`,
  uses `_updatedAtIndex` instead.

Server-side:
- mana-ai iteration-writer no longer emits `updatedAt` in
  sync_changes.data; receivers derive it from the field-meta map.
- mana-sync types: no change (the wire format already uses
  `field_meta` / `at` from F1).

Out of scope: backend Drizzle schemas (mana-credits, mana-events, …)
keep their `updated_at` columns. Those are pure server-internal — not
part of the sync_changes / __fieldMeta mechanism F3 cleans up.

Tests + checks:
- 0 svelte-check errors over 7652 files.
- 29/29 sync.test.ts (vitest).
- 61 mana-ai bun tests.
- mana-sync go test ./... cached green.

Plan: docs/plans/sync-field-meta-overhaul.md F3.

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

docs/plans/sync-field-meta-overhaul.md

@@ -146,8 +146,8 @@ _Wird befüllt während der Ausführung._
 | Phase | Commit | Notiz |
 | --- | --- | --- |
 | F1 | `7766ea502` | Web + mana-sync (Go) + mana-ai + apps/api/mcp + tests + DB schema reset. **Note: Commit-Titel `docs(plans): mark llm-fallback-aliases SHIPPED` ist irreführend — Multi-Terminal-Race hat F1 in einem fremden Commit zusammengeführt. Code ist trotzdem korrekt drin (27 F1 Files + Plan).** Tests grün, DB migriert. |
-| F2 | _staged, uncommitted_ | Origin-Gate aktiviert. `originFromActor()` in shared-ai/field-meta.ts maps actor.kind → 'user'/'agent'/'system'/'migration'. Hooks nutzen es. Repair-Migrations (repair-silent-twin, legacy-avatar) wrappen ihre Writes in `runAsAsync(systemMigrationActor, ...)`. `applyServerChanges` bekommt `ApplyServerChangesOptions.isInitialHydration` Parameter, beide Caller (push-response + pull) setzen ihn aus dem Cursor-State. Conflict-Trigger feuert nur noch wenn `localMeta[k]?.origin === 'user' && !options.isInitialHydration`. **29 Tests grün** inkl. 4 neuer (replay-burst no-conflict, agent-origin no-conflict, hydration no-conflict, user-edit fires-conflict). |
-| F3 | _pending_ | |
+| F2 | `ad5e04a55` | Origin-Gate aktiviert. `originFromActor()` in shared-ai/field-meta.ts maps actor.kind → 'user'/'agent'/'system'/'migration'. Hooks nutzen es. Repair-Migrations (repair-silent-twin, legacy-avatar) wrappen ihre Writes in `runAsAsync(systemMigrationActor, ...)`. `applyServerChanges` bekommt `ApplyServerChangesOptions.isInitialHydration` Parameter, beide Caller (push-response + pull) setzen ihn aus dem Cursor-State. Conflict-Trigger feuert nur noch wenn `localMeta[k]?.origin === 'user' && !options.isInitialHydration`. **29 Tests grün** inkl. 4 neuer (replay-burst no-conflict, agent-origin no-conflict, hydration no-conflict, user-edit fires-conflict). |
+| F3 | _staged, uncommitted_ | `updatedAt` aus dem Sync-Wire entfernt, durch zwei orthogonale Mechanismen ersetzt: (1) `_updatedAtIndex` als lokale, nicht-syncbare Schatten-Spalte die der Dexie-Hook (creating/updating) auf jedem Write stempelt — Dexie v53 indexiert sie auf 22 Tabellen die früher `updatedAt` indexiert hatten. (2) `deriveUpdatedAt(record)` als read-side Computed = `max(__fieldMeta[*].at)` für 60+ Type-Converter die einen public `updatedAt: string` zurückliefern. Module-Stores: 121 Files, ~382 Stamping-Sites entfernt (regex-codemod). Local-Types: 43 Files, `updatedAt: string` aus Local-prefixed Interfaces entfernt (Public-Types behalten ihn als computed). `applyServerChanges` setzt `_updatedAtIndex` selbst beim Replay (mit `max(serverFields.at)` oder dem record-time). mana-ai/iteration-writer schreibt kein `updatedAt` mehr ins Wire-`data`. **Skipped:** Drizzle-Schemas der 11 Backend-Services — die `updated_at` Spalten dort sind nicht sync-relevant (pure server-internal columns) und wurden nicht in F3 angetastet. **0 svelte-check errors** über 7652 Files, 29/29 sync.test.ts grün, 61 mana-ai bun tests grün, mana-sync go tests grün. |
 | F4 | _pending_ | |
 | F5 | _pending_ | |
 | F6 | _pending_ | |