feat(git-sync): CommonJS build + §13.1 editor-ext idempotency gate (Phase A.2)

Make @docmost/git-sync natively consumable by the CommonJS server (and jest):
build to CommonJS (tsconfig module CommonJS, drop type:module, strip .js from
relative imports), and lazy-load the only ESM-only dep (marked) via the dynamic
Function('import()') trick (mirrors docmost-client.loader.ts) with a require()
fallback so vitest's evaluator works too. git-sync tests stay green (314 pass,
3 expected fail).

Add the §13.1 idempotency gate (apps/server .../git-sync-converter-gate.spec.ts):
13 editor-ext docs (paragraphs/headings, marks, links, bullet/ordered/task lists,
blockquote, callouts, code block, hr, table, nested mix) round-trip
content(editor-ext) -> convertProseMirrorToMarkdown -> markdownToProseMirror ->
TiptapTransformer.toYdoc/fromYdoc(tiptapExtensions) -> canonicalize and assert
docsCanonicallyEqual. All green => the vendored converter's docmost-schema is
schema-compatible with editor-ext (no node/mark/attr loss), which the plan §13.1
requires before Phase B. The one intrinsic markdown-image lossiness (width/height
/align can't ride plain ![](src)) is isolated in a KNOWN DIVERGENCE block, not
hidden. Server tsc clean.

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

packages/git-sync/build/engine/loop-guard.js

@@ -1,3 +1,6 @@
+"use strict";
+Object.defineProperty(exports, "__esModule", { value: true });
+exports.bodyHash = bodyHash;
 /**
  * Loop-guard primitives (SPEC §10). The sync engine must never re-pull its OWN
  * write as if it were a remote edit: after a push, the next poll will see the
@@ -10,7 +13,7 @@
  * to decide "this is our own write, ignore it") is a future increment — here we
  * only PRODUCE the hash and the per-page push record (see `src/push.ts`).
  */
-import { createHash } from "node:crypto";
+const node_crypto_1 = require("node:crypto");
 /**
  * Stable hash of a page's markdown BODY (SPEC §10 "хэш тела"). Deterministic:
  * the same input string always yields the same digest, a different input a
@@ -23,6 +26,6 @@ import { createHash } from "node:crypto";
  * caller is responsible for passing a canonical/stable representation if it
  * wants hash equality across cosmetic-only differences.
  */
-export function bodyHash(markdownBody) {
-    return createHash("sha256").update(markdownBody, "utf8").digest("hex");
+function bodyHash(markdownBody) {
+    return (0, node_crypto_1.createHash)("sha256").update(markdownBody, "utf8").digest("hex");
 }