split: sync-engine rewrite (sync-operations + sync-client.ts)

Replace the single unrestricted-syncer.ts with a two-loop architecture:
- syncer.ts drains the FIFO wire queue (HTTP + WS handlers).
- reconciler.ts moves files to make localPath match remoteRelativePath
  (topo-sorted move graph, in-memory cycle resolution with crash-safe
  swap markers).
- sync-event-queue.ts holds the byDocId / byLocalPath indexes and the
  pending-create promise chain.
- offline-change-detector.ts, expected-fs-events.ts, types.ts, and a
  rewritten cursor-tracker.ts / file-change-notifier.ts round it out.
Plus sync-client.ts wiring, tracing/sync-history.ts updates, index.ts
re-exports, and sync-client tsconfig/webpack/package.json.

frontend/sync-client/package.json

@@ -14,19 +14,17 @@
     },
     "devDependencies": {
         "byte-base64": "^1.1.0",
-        "minimatch": "^10.0.1",
-        "p-queue": "^8.1.0",
+        "minimatch": "^10.1.1",
+        "p-queue": "^9.0.1",
         "reconcile-text": "^0.8.0",
-        "uuid": "^13.0.0",
-        "@types/node": "^24.8.1",
-        "ts-loader": "^9.5.2",
+        "@types/node": "^25.0.2",
+        "ts-loader": "^9.5.4",
         "tslib": "2.8.1",
-        "tsx": "^4.20.6",
-        "typescript": "5.8.3",
-        "webpack": "^5.99.9",
+        "tsx": "^4.21.0",
+        "typescript": "5.9.3",
+        "webpack": "^5.103.0",
         "webpack-cli": "^6.0.1",
         "webpack-merge": "^6.0.1",
-        "@sentry/browser": "^10.8.0",
-        "ws": "^8.18.3"
+        "@sentry/browser": "^10.30.0"
     }
 }