fix(engine,dashboard): close 7 review findings on merger auto-sync

Data-loss fixes in syncWorktreeToHead:
  - Untracked-restore checks `git ls-tree -r --name-only HEAD` to skip
    paths the new tip added as tracked files; user bytes stay in the
    stage dir instead of clobbering merged content.
  - Apply-failure on a deleted/renamed file: conflictedFiles falls back
    to parsing `diff --git a/<p> b/<p>` headers when --diff-filter=U
    returns nothing.
  - All git invocations pass `-c core.quotePath=false` so non-ASCII
    paths round-trip through copyFileSync.
  - Stash-and-ff re-verifies rev-parse HEAD === newSha right before
    each `reset --hard HEAD` (TOCTOU). On mismatch we bail with patch
    preserved on disk.
  - Stage dir lifecycle moved into try/finally with preserveStageDir
    flag — kept whenever the user's edits live only in patchPath; rm'd
    on all clean exits.
  - Patch written to disk before the apply attempt, not only on
    failure, so a crash between snapshot and apply doesn't lose edits.

Multi-worktree-same-branch fix:
  - New getRegisteredWorktreeBranches returns Array<{branch,path}>
    instead of collapsing into a Map. Multiple worktrees can share a
    branch via `git worktree add --force -b`; merger now syncs all of
    them rather than silently skipping all but the last.

Contract + surfacing fixes:
  - JSDoc on merge:auto-sync GitMutationType now lists the actually-
    emitted outcome strings + stage enum.
  - GET /api/tasks/merge-advance-events joins merge:auto-sync events
    within ±5min of the advance and returns them in a new
    `autoSync: AutoSyncOutcome[]` field; useMergeAdvanceNotice exposes
    the same shape so the banner can surface pop-conflicts (including
    patchPath) instead of dropping them.

Hygiene:
  - Merger now reads the setting via normalizeMergeAdvanceAutoSyncMode
    instead of an inline check + `as unknown` cast.

New tests:
  - Untracked-collides-with-tracked preserves merged content.
  - Apply failure on deleted file populates conflictedFiles from
    patch header.
  - Route surfaces autoSync outcomes (clean-sync + pop-conflict)
    joined within the time window.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

packages/engine/src/run-audit.ts

@@ -238,21 +238,29 @@ export type GitMutationType =
    *   newSha?: string;
    *   worktreePath?: string;
    *   outcome:
-   *     | "clean-pull"
-   *     | "stash-pull-pop"
-   *     | "stash-pop-conflict"
-   *     | "skipped-dirty"
-   *     | "skipped-not-on-branch"
-   *     | "failed"
-   *     | "enumeration-failed"
-   *     | "exception";
-   *   stashSha?: string;
-   *   stashLabel?: string;
-   *   conflictedFiles?: string[];
-   *   stage?: "stash" | "pull" | "pop";
+   *     | "clean-sync"                  // worktree was clean against previousSha; reset --hard HEAD snapped it forward
+   *     | "synced-with-edits-restored"  // real edits captured as patch, snapped to HEAD, patch re-applied cleanly
+   *     | "synced-with-pop-conflict"    // patch failed to reapply OR untracked file collided with newly-tracked path
+   *     | "skipped-dirty"               // ff-only mode + real edits → no-op (banner surfaces for manual handling)
+   *     | "skipped-not-on-branch"       // worktree's HEAD is on a different branch than integrationBranch
+   *     | "skipped-head-not-at-new-sha" // concurrent advance moved HEAD past newSha between guard and reset
+   *     | "failed"                      // git command exited non-zero; see stage + error
+   *     | "enumeration-failed"          // `git worktree list --porcelain` failed in the project root
+   *     | "exception";                  // syncWorktreeToHead threw outside its own try/catch
+   *   stashedFiles?: string[];          // tracked-file edits captured into patchPath
+   *   patchPath?: string;               // /tmp/fusion-worktree-sync-<id>/edits.patch (preserved when outcome surfaces a conflict)
+   *   conflictedFiles?: string[];       // paths git apply --3way couldn't reconcile; falls back to patch-header parsing when the index has no unmerged entries
+   *   untrackedRestored?: string[];     // untracked files copied back into the worktree after the snap
+   *   untrackedSkippedAsTracked?: string[]; // untracked files whose paths collided with newly-tracked files at HEAD; left in the stage dir
+   *   stage?: "snapshot" | "reset" | "apply" | "untracked-restore"; // only on outcome === "failed"
    *   error?: string;
    * }
    * ```
+   *
+   * Per-step `pull:fast-forward`, `stash:push`, `stash:pop`, and
+   * `stash:pop-conflict` events that flow through the merger's auditor as
+   * part of this auto-sync carry `metadata.autoSync = true` so consumers can
+   * filter them apart from user-triggered git operations.
    */
   | "merge:auto-sync"
   /**