PR #6656 added rel_path + \x00 prefixing to ``bundle_content_hash`` so a
filename swap between two files in a bundle changes the digest. But it
only patched the in-memory side — ``content_hash`` in ``tools/skills_guard.py``
(the on-disk equivalent) still hashed file contents only.
These two functions need to stay symmetric: ``check_for_skill_updates``
compares the disk hash of an installed skill against the bundle hash
of the upstream copy. With the asymmetric fix, every clean install
showed as drifted because the digests no longer matched
(2 existing tests in ``test_skills_hub.py`` started failing as soon as
the contributor's change landed).
Apply the same ``rel_path + \x00 + content`` shape to the disk-side
function. Both functions now produce the same digest for the same skill
content laid out two ways. Documented the symmetry invariant in the
docstring so a future change to either function knows to touch both.
Also adds tests/tools/test_pr_6656_regressions.py with 10 regression
tests covering all three fixes salvaged in PR #6656:
- uninstall_skill path traversal (4 cases: parent segments, absolute
paths, symlink escape, legitimate skill)
- bundle_content_hash filename swap detection (4 cases: in-memory
swap, identity, disk-side swap, bundle↔disk symmetry)
- list_pending lock contract (2 cases: source-grep contract, smoke)
Also fixes AUTHOR_MAP entry for @aaronlab — their commit email
(1115117931@qq.com) maps to "aaronagent" which isn't a real GitHub
login, so changelog @mentions would 404.
