fix(git-sync): address PR #119 review (#1571)

Resolve the code-review findings from comment #1571 on PR #119.

Engine (packages/git-sync):
- Idempotent CREATE on retry: before createPage, look the page up in the
  live Docmost tree by (parentPageId, title) and ADOPT it instead of
  duplicating when a prior cycle created it but failed to persist the
  pageId back to disk. Only trust a COMPLETE tree for the lookup; fall
  back to createPage otherwise. Covered by new tests incl. a complete=false
  regression-lock.
- Route applyPullActions diagnostics through an injected logger instead of
  bare console (thread log from the cycle).
- Add a timeout to the git execFile chokepoint (runRaw) so a hung git
  subprocess cannot wedge a sync cycle.
- Translate remaining Russian code comments to English.
- Remove dead standalone-CLI code (parseArgs/PushParsedArgs,
  parseSettings/envSchema, loadSettingsOrExit + config-errors.ts) and the
  matching index exports/specs; keep the Settings type.
- Fix the dangling docs link in package.json.
- Add a schema-surface snapshot guard so any drift in the vendored
  document schema is a loud, must-review CI failure (+ provenance header).

Server (apps/server):
- Add a configurable watchdog timeout to the spawned git http-backend so a
  stalled push cannot hold the per-space lock forever
  (GIT_SYNC_BACKEND_TIMEOUT_MS).
- Close the in-process TOCTOU window in SpaceLockService.withSpaceLock by
  reserving the slot synchronously before acquire.
- Add tests: removePage git-sync provenance (both branches), ensureServable
  force-push-protection git configs, and the phase-B+ datasource methods.

Docs / build:
- AGENTS.md: list git-sync as the fifth workspace package and note the
  three schema mirrors; fix the dangling git-sync-plan.md backlog link.
- pnpm-lock.yaml: add the missing @docmost/git-sync workspace link so
  pnpm install --frozen-lockfile (CI default) succeeds.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

packages/git-sync/test/engine-gaps.test.ts

@@ -263,6 +263,7 @@ describe('applyPushActions (push.ts) — move prefetch isolation', () => {
 
   function makeClient() {
     return {
+      listSpaceTree: vi.fn(async () => ({ pages: [], complete: true })),
       importPageMarkdown: vi.fn(async () => ({ updatedAt: 'u' })),
       createPage: vi.fn(async () => ({ data: { id: 'new-id' } })),
       deletePage: vi.fn(async () => ({})),