feat(sync): complete incremental sync protocol with storage-pull, state management, and tests (#799)

- Add storage-pull strategy: rclone-based sync from remote storage with
  overlay and clean modes, URI parsing (storage://remote:bucket/path),
  transfer parallelism, and automatic rclone availability checking
- Add SyncStateManager: persistent state load/save with configurable
  paths, workspace hash calculation via SHA-256 of key project files,
  and drift detection for external modification awareness
- Add action.yml inputs: syncStrategy, syncInputRef, syncStorageRemote,
  syncRevertAfter, syncStatePath with sensible defaults
- Wire sync into Input (5 getters), BuildParameters (5 fields), index.ts
  (local build path), and RemoteClient (orchestrator path) with post-job
  overlay revert when syncRevertAfter is true
- Add 42 unit tests covering all strategies, URI parsing, state
  management, hash calculation, drift detection, error handling, and
  edge cases (missing rclone, invalid URIs, absent state, empty diffs)
- Add root:true to eslintrc to prevent plugin resolution conflicts

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/model/input.ts

@@ -241,6 +241,28 @@ class Input {
     return Input.getInput('dockerWorkspacePath') ?? '/github/workspace';
   }
 
+  static get syncStrategy(): string {
+    return Input.getInput('syncStrategy') ?? 'full';
+  }
+
+  static get syncInputRef(): string {
+    return Input.getInput('syncInputRef') ?? '';
+  }
+
+  static get syncStorageRemote(): string {
+    return Input.getInput('syncStorageRemote') ?? '';
+  }
+
+  static get syncRevertAfter(): boolean {
+    const input = Input.getInput('syncRevertAfter') ?? 'true';
+
+    return input === 'true';
+  }
+
+  static get syncStatePath(): string {
+    return Input.getInput('syncStatePath') ?? '.game-ci/sync-state.json';
+  }
+
   static get dockerCpuLimit(): string {
     return Input.getInput('dockerCpuLimit') ?? os.cpus().length.toString();
   }