fix(termux): resolve packed-refs and worktree refs in skill-sync fingerprint

The bundled-skill sync stamp added in the cherry-picked salvage commit
parsed .git/HEAD and looked for a loose ref file in the worktree gitdir
only, so two real cases hit the unresolved branch:

- repos after `git gc` where active refs live in packed-refs
- linked worktrees, whose branch ref lives in <commondir>/refs/heads/
  (verified on the worktree this salvage was built in)

Both fell back to a constant-string fingerprint, so post-commit launches
would never re-run the real skill sync. Now we resolve packed-refs and
check both the worktree gitdir and the common dir for loose refs.

Adds three tests covering: packed-refs resolution, worktree common-dir
packed lookup, worktree common-dir loose lookup, and the explicit
'unresolved' marker (still stable + version-fallback-safe).

tests/hermes_cli/test_tui_resume_flow.py

@@ -428,6 +428,88 @@ def test_termux_forced_bundled_skill_sync_runs(monkeypatch, tmp_path, main_mod):
     assert calls == [True]
 
 
+def test_read_git_revision_fingerprint_resolves_packed_refs(tmp_path, main_mod):
+    repo = tmp_path / "repo"
+    git_dir = repo / ".git"
+    git_dir.mkdir(parents=True)
+    (git_dir / "HEAD").write_text("ref: refs/heads/main\n", encoding="utf-8")
+    packed_sha = "1234567890abcdef1234567890abcdef12345678"
+    (git_dir / "packed-refs").write_text(
+        "# pack-refs with: peeled fully-peeled sorted\n"
+        f"{packed_sha} refs/heads/main\n"
+        "abcdef0000000000000000000000000000000000 refs/tags/v1.0\n"
+        "^99999999aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa\n",
+        encoding="utf-8",
+    )
+
+    fingerprint = main_mod._read_git_revision_fingerprint(repo)
+
+    assert fingerprint == f"git:refs/heads/main:{packed_sha}"
+
+
+def test_read_git_revision_fingerprint_packed_refs_in_worktree_common_dir(
+    tmp_path, main_mod
+):
+    main_repo = tmp_path / "repo"
+    common_git = main_repo / ".git"
+    common_git.mkdir(parents=True)
+    packed_sha = "fedcba9876543210fedcba9876543210fedcba98"
+    (common_git / "packed-refs").write_text(
+        f"{packed_sha} refs/heads/main\n",
+        encoding="utf-8",
+    )
+
+    worktree = tmp_path / "wt"
+    worktree.mkdir()
+    wt_gitdir = common_git / "worktrees" / "wt"
+    wt_gitdir.mkdir(parents=True)
+    (wt_gitdir / "HEAD").write_text("ref: refs/heads/main\n", encoding="utf-8")
+    (wt_gitdir / "commondir").write_text("../..\n", encoding="utf-8")
+    (worktree / ".git").write_text(f"gitdir: {wt_gitdir}\n", encoding="utf-8")
+
+    fingerprint = main_mod._read_git_revision_fingerprint(worktree)
+
+    assert fingerprint == f"git:refs/heads/main:{packed_sha}"
+
+
+def test_read_git_revision_fingerprint_loose_ref_in_worktree_common_dir(
+    tmp_path, main_mod
+):
+    """`git worktree add -b NAME` writes the new branch ref to the common dir,
+    not the per-worktree gitdir. The fingerprint must still resolve it."""
+    main_repo = tmp_path / "repo"
+    common_git = main_repo / ".git"
+    common_git.mkdir(parents=True)
+    loose_sha = "0123456789abcdef0123456789abcdef01234567"
+    (common_git / "refs" / "heads").mkdir(parents=True)
+    (common_git / "refs" / "heads" / "feature").write_text(
+        loose_sha + "\n", encoding="utf-8"
+    )
+
+    worktree = tmp_path / "wt"
+    worktree.mkdir()
+    wt_gitdir = common_git / "worktrees" / "wt"
+    wt_gitdir.mkdir(parents=True)
+    (wt_gitdir / "HEAD").write_text("ref: refs/heads/feature\n", encoding="utf-8")
+    (wt_gitdir / "commondir").write_text("../..\n", encoding="utf-8")
+    (worktree / ".git").write_text(f"gitdir: {wt_gitdir}\n", encoding="utf-8")
+
+    fingerprint = main_mod._read_git_revision_fingerprint(worktree)
+
+    assert fingerprint == f"git:refs/heads/feature:{loose_sha}"
+
+
+def test_read_git_revision_fingerprint_unresolved_ref_is_stable(tmp_path, main_mod):
+    repo = tmp_path / "repo"
+    git_dir = repo / ".git"
+    git_dir.mkdir(parents=True)
+    (git_dir / "HEAD").write_text("ref: refs/heads/missing\n", encoding="utf-8")
+
+    fingerprint = main_mod._read_git_revision_fingerprint(repo)
+
+    assert fingerprint == "git:refs/heads/missing:unresolved"
+
+
 def test_main_top_level_oneshot_accepts_toolsets(monkeypatch, main_mod):
     captured = {}