fix(uninstall): remove graphify hook/section from Claude local-only files (#1731)

[TPAteeq]

Fixes #1731.

Problem

graphify uninstall (and graphify claude uninstall) only touched
.claude/settings.json and the root CLAUDE.md. If a user relocates the
PreToolUse hook into .claude/settings.local.json and the ## graphify
instructions into CLAUDE.local.md / .claude/CLAUDE.local.md — a common move
so graphify's config isn't committed to a shared repo — uninstall skipped both
and reported "nothing to do", leaving them behind.

Fix

• _uninstall_claude_hook strips the hook from both settings.json and
  settings.local.json (new shared helper _strip_graphify_hook).
• claude_uninstall strips the ## graphify section from CLAUDE.md, root
  CLAUDE.local.md, and .claude/CLAUDE.local.md (new shared helper
  _strip_graphify_md_section). It cleans every file that's present rather than
  the first one found, and always runs the hook cleanup afterward.
• _strip_graphify_md_section reads the two newly-covered local files
  defensively, so a non-UTF-8 or unreadable file can't abort uninstall.

Unrelated local-only files (no graphify content) are left byte-for-byte
untouched, and the existing "nothing to do" / "not found" messaging is preserved.

Out of scope

The issue also suggests an install-side --local flag to write directly into
the local-only files. That's a feature and a separate design decision; this PR
only makes uninstall symmetric with wherever the config actually lives.

Testing

Six regression tests added in tests/test_claude_md.py covering the hook in
settings.local.json, the section in both CLAUDE.local.md locations, the
"section in both standard and local" case, content preservation, and an
unreadable (non-UTF-8) local file. Full test suite passes.

[safishamsi]

Merged into v8 (0d206cb), authorship preserved — thanks @TPAteeq. Clean helper extraction (_strip_graphify_hook / _strip_graphify_md_section), cleans all present files (not short-circuited), deletes emptied files, tolerates non-UTF-8, and preserves other content. I verified both entry points the issue names: graphify claude uninstall and the bare graphify uninstall (uninstall_all) both now clean .claude/settings.local.json and .claude/CLAUDE.local.md. Full suite green (3089 passed).