refactor(git-sync): address PR #119 review #3 — honest gitRemote scaffolding comments, env example, shared ESM bridge

1. gitRemote is NOT yet consumed (the vendored engine has no remote-push path,
   SPEC §7). Corrected the buildSettings docstring (it wrongly called gitRemote
   "load-bearing") and marked the env -> validation -> getter -> buildSettings
   chain as inert SCAFFOLDING for the deferred remote-push feature at all three
   sites. Kept the wiring (harmless; removing only churns).

2. .env.example: document that GIT_SYNC_REMOTE_TEMPLATE substitutes the literal
   "{spaceId}" per-space (with the example), so an operator doesn't point every
   space at one remote.

3. Extracted the copy-pasted CJS->ESM dynamic-import bridge
   (`new Function('s','return import(s)')`) into one shared
   common/helpers/esm-import.ts; git-sync.loader, docmost-client.loader and
   mcp.service now import it and keep their own typed loadX() wrappers.

Deferred (notes only, not implemented):
- lcs.ts + three-way-merge.ts could move into packages/git-sync, but that engine
  is vendored (manual re-sync) — added a one-line note at three-way-merge.ts to
  revisit once the re-sync story is settled.
- schema-core single source + BullMQ/fencing remain documented from prior rounds.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

apps/server/src/integrations/git-sync/services/git-sync.orchestrator.ts

@@ -111,10 +111,20 @@ export class GitSyncOrchestrator implements OnModuleInit, OnModuleDestroy {
   /**
    * Build the engine `Settings` for a space. The engine's REST-era fields
    * (docmostApiUrl/email/password) are unused on the native path — the
-   * datasource writes in-process — so they are placeholders; only `vaultPath`,
-   * `gitRemote`, and the tunables are load-bearing.
+   * datasource writes in-process — so they are placeholders; only `vaultPath`
+   * and the tunables are load-bearing today.
+   *
+   * `gitRemote` is NOT yet consumed: the vendored engine has no remote-push path
+   * (see engine/git.ts, engine/pull.ts, SPEC §7 — remote push is deferred), so
+   * the GIT_SYNC_REMOTE_TEMPLATE env -> validation -> getter -> this field chain
+   * is inert SCAFFOLDING kept in place for the future remote-push feature. It is
+   * harmless (the engine ignores it) and removing it would only churn; we still
+   * populate it so the wiring is ready when the engine grows a push path.
    */
   private async buildSettings(spaceId: string): Promise<Settings> {
+    // Scaffolding for the deferred remote-push feature — the engine does not read
+    // `gitRemote` yet (see the docstring above). Substitute {spaceId} per-space so
+    // the value is correct the moment the engine starts consuming it.
     const remoteTemplate = this.environmentService.getGitSyncRemoteTemplate();
     const gitRemote = remoteTemplate
       ? remoteTemplate.replace(/\{spaceId\}/g, spaceId)