fix(security-guidance): support Windows venv layout so the agentic reviewer works on win32

[mholovetskyi]

Problem

security-guidance's strongest layer — the agentic commit reviewer — is unavailable on Windows unless claude_agent_sdk happens to be system-installed. The SessionStart bootstrap (hooks/ensure_agent_sdk.py) returns SKIP_WIN32 early, and the skip's own comment explains why: "Windows venv layout (Lib/site-packages, no python subdir) isn't handled by the consumer's glob."* The consumer fallbacks in hooks/llm.py glob only the POSIX layout (lib/python*/site-packages), and venv_py assumed bin/python.

This PR closes that annotated gap end-to-end rather than working around it.

Fix

• llm.py (both SDK-fallback sites): additionally glob the Windows layout Lib/site-packages (no python* subdir). On POSIX the extra glob matches nothing; on Windows the original glob matches nothing — no behavior change on either platform beyond enabling the intended fallback.
• ensure_agent_sdk.py: select the venv interpreter as Scripts/python.exe on win32 (bin/python elsewhere) and remove the early-return. The SKIP_WIN32 outcome code is retained but never emitted, so sdk_bootstrap telemetry rows from older plugin versions keep their meaning; new Windows rows will now report the same BUILT/NOOP/BUILD_FAILED codes as POSIX, and the existing err_phase/err_kind fingerprinting applies unchanged.

Everything else in the bootstrap is already platform-neutral (the O_EXCL sentinel lock, timeouts, pip invocation via the venv interpreter).

Tested on Windows 11 (Python 3.13.14)

Bootstrap, run twice against a scratch SECURITY_WARNINGS_STATE_DIR:

--- RUN 1 ---
{"async": true, "asyncTimeout": 180000}
{"metrics": {"sdk_bootstrap": 2, "sdk_bootstrap_ms": 51440, "pv": 20000}}   # BUILT
--- RUN 2 ---
{"async": true, "asyncTimeout": 180000}
{"metrics": {"sdk_bootstrap": 1, "sdk_bootstrap_ms": 5191, "pv": 20000}}    # NOOP_VENV

Consumer glob, against the venv built above:

OLD glob matches: []
NEW glob matches: ['...\agent-sdk-venv\Lib\site-packages']
claude_agent_sdk imported OK from: ...\Lib\site-packages\claude_agent_sdk\__init__.py

i.e. the pre-fix glob cannot see a Windows venv at all (confirming why the skip existed), and the new glob finds it and the SDK imports through it. py_compile passes on both files.

Notes

• No competing PR touches this (searched ensure_agent_sdk, agent-sdk-venv, SKIP_WIN32, security-guidance windows); the existing Windows-related PRs (fix(security-guidance): normalize CLAUDE_PLUGIN_ROOT path separators on Windows #68694, fix(security-guidance): strip CRLF from Python version probe on Windows #68701, fix(security-guidance): use a cross-platform Python launcher #47502) address path separators, CRLF, and the launcher — not the venv bootstrap.
• platform:windows is one of the largest open-issue label groups; this restores the plugin's headline feature for that entire user class.

🤖 Generated with Claude Code