feat: raw capture / raw status / --replaces-bundle - documentation from git repositories as a bundle, with drift reporting (#177)

New repo_capture module: resolve a branch or tag-pattern ref rule, fetch it
shallowly by name into a bare cache, read the glob-selected files as blobs,
and record repo/ref/commit/globs/capture fields in _capture.json. raw status
reports changed captured bundles as A/M/D; raw accept --replaces-bundle swaps
a captured bundle for its new edition at the same address. iter_raw_files now
skips _capture.json and anchors the CONTRACT.md exclusion to raw/CONTRACT.md.

Files changed:
- .gitignore
- CHANGES.md
- README.md
- VERSION
- instructions/wiki-ingest/SKILL.md
- raw/CONTRACT.md
- tools/CONTRACT.md
- tools/README.md
- tools/chemenu/cli_contract.py
- tools/chemenu/commands/dist_cmd.py
- tools/chemenu/commands/docs_verify.py
- tools/chemenu/commands/raw_cmd.py
- tools/chemenu/config.py
- tools/chemenu/repo_capture.py
- tools/chemenu/tests/test_cli.py
- tools/chemenu/tests/test_raw_capture.py

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01SnAJ7Z3CpVD3PRbN73QtU2

.gitignore

@@ -73,6 +73,11 @@ npm-debug.log*
 # "Gates") - local, per-session, never committed
 /tools/.wikitool_session/
 
+# `wikitool raw capture`/`raw status` git cache (see raw/CONTRACT.md "Getting a
+# repository in") - one bare repository per captured URL, refetched on demand.
+# Derived and per-checkout; never committed, never shipped.
+/tools/.wikitool_capture/
+
 # Go
 /go.mod
 /go.sum