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>

apps/server/src/integrations/git-sync/http/git-http-backend.service.ts

@@ -176,6 +176,45 @@ export class GitHttpBackendService {
         return done();
       }
 
+      // Watchdog: a client that opens git-receive-pack and stalls keeps the
+      // child alive forever, so run() never resolves and (because this runs
+      // inside withSpaceLock) the per-space lock is held + heartbeat-refreshed
+      // indefinitely. Bound the request: on expiry kill the child, send a clean
+      // 500 if nothing was sent yet, and settle the promise. The log carries no
+      // client echo / credentials / body. `.unref()` so the timer never keeps the
+      // event loop alive; ALWAYS cleared in the close/error handlers below.
+      const timer = setTimeout(() => {
+        this.logger.warn(
+          `git http-backend timed out after ` +
+            `${this.environmentService.getGitSyncBackendTimeoutMs()}ms; killing child`,
+        );
+        try {
+          child.kill('SIGTERM');
+          // Escalate to SIGKILL shortly after in case SIGTERM is ignored.
+          const sigkill = setTimeout(() => {
+            try {
+              child.kill('SIGKILL');
+            } catch {
+              /* ignore */
+            }
+          }, 2000);
+          sigkill.unref?.();
+        } catch {
+          /* ignore */
+        }
+        if (!headerParsed && !rawRes.headersSent) {
+          this.send500(rawRes, 'timeout');
+        } else {
+          try {
+            rawRes.end();
+          } catch {
+            /* ignore */
+          }
+        }
+        done();
+      }, this.environmentService.getGitSyncBackendTimeoutMs());
+      timer.unref?.();
+
       // Accumulate stdout until we have the full CGI header block, then write the
       // parsed status/headers and start streaming the remaining body bytes.
       let headerParsed = false;
@@ -221,6 +260,7 @@ export class GitHttpBackendService {
       });
 
       child.on('error', (err) => {
+        clearTimeout(timer);
         if (!headerParsed && !rawRes.headersSent) {
           this.send500(rawRes, 'child-error', err);
         } else {
@@ -235,6 +275,7 @@ export class GitHttpBackendService {
       });
 
       child.on('close', (code) => {
+        clearTimeout(timer);
         if (!headerParsed && !rawRes.headersSent) {
           // The child exited before emitting a complete CGI header block.
           this.logger.error(