fix: wrap plugin hooks in a top-level "hooks" key so Claude Code loads them

[zackkatz]

Linked issue

No open issue. Current Claude Code reports this when it loads the plugin:

Failed to load hooks from .../code-review-graph/<sha>/hooks/hooks.json:
[ { "code": "custom", "path": [], "message": "hooks.json must have 'hooks' (the hook matchers) or 'modules' (hooks modules), or both" } ]

What & why

hooks/hooks.json holds a bare event map ({"SessionStart": [...], "PostToolUse": [...]}). Claude Code requires a plugin hooks file to put that map under a top-level "hooks" key, so it skips the file and none of the plugin's hooks run.

The plugins reference states it directly:

A hooks file wraps the event map in a top-level "hooks" key, the shape hooks/hooks.json uses. A file that contains only the event map, without that wrapper, fails to load.

The wrapper was in this file until 66ccaef (#283). The error in #283 came from a settings.json written by the installer and listed hooks: Expected array, but received undefined under each event, which points to the missing matcher/hooks entries. 66ccaef fixed those and also removed the wrapper. This PR puts the wrapper back and keeps the matchers.

Changes:

• hooks/hooks.json: event map moved under "hooks". Matchers, commands, and timeouts are unchanged.
• tests/test_packaging.py and tests/test_skills.py: both read the shipped file, so they now expect the wrapper. The packaging test fails if the wrapper is removed again.
• CHANGELOG.md: entry under Unreleased.

How it was tested

Claude Code loading the plugin (Claude Code 2.1.294, claude --plugin-dir <checkout> -p "reply ok" --debug-file <log>):

Checkout	Debug log
staging before this PR	[ERROR] "Failed to load hooks for crg: ... hooks.json must have \hooks` (the hook matchers) or `modules` (hooks modules), or both"andRegistered 15 hooks from 23 plugins`
This branch	No error. Registered 18 hooks from 23 plugins

The difference of 3 is this plugin's SessionStart hook plus its two PostToolUse hooks.

claude plugin validate . passes on both versions, so it does not catch this. Only loading the plugin shows the error.

Test suite:

uv run pytest tests/ --tb=short -q
# 1 failed, 4267 passed, 850 skipped, 2 xfailed, 2 xpassed

The one failure is tests/test_embedding_initialization.py::test_windows_server_still_prewarms_before_mcp_run (NameError: name 'windows_events' is not defined). It fails the same way on unmodified staging on macOS and is not related to this change.

uv run pytest tests/test_packaging.py -m packaging -k hook_template -q
# this branch: 1 passed
# same test with the old hooks.json: 1 failed
#   AssertionError: shipped hook template must wrap its events in 'hooks': ['PostToolUse', 'SessionStart']

uv run ruff check tests/test_packaging.py
# All checks passed!

Checklist

• Tests added for new functionality
• All tests pass: uv run pytest tests/ --tb=short -q (except the Windows test above, which also fails on staging)
• Linting passes
• Type checking: no Python source in code_review_graph/ changed
• Lines are at most 100 characters
• Docs updated where behavior changed (CHANGELOG)