* fix(hooks): detect Claude Code via stdin session_id, not filtered env (#2520)
The #2344 fix assumed `CLAUDECODE` would propagate to hook subprocesses.
On Claude Code v2.1.116 it doesn't — Claude Code applies a separate env
filter to PreToolUse hook commands that drops bare CLAUDECODE and
CLAUDE_SESSION_ID, keeping only CLAUDE_CODE_*-prefixed vars plus
CLAUDE_PROJECT_DIR. As a result every Edit/Write on an existing file
produced a redundant READ-BEFORE-EDIT advisory inside Claude Code.
Use `data.session_id` from the hook's stdin JSON as the primary Claude
Code signal (it's part of Claude Code's documented PreToolUse hook-input
schema). Keep CLAUDE_CODE_ENTRYPOINT / CLAUDE_CODE_SSE_PORT env checks
as propagation-verified fallbacks, and keep the legacy
CLAUDE_SESSION_ID / CLAUDECODE checks for back-compat and
future-proofing.
Add tests/bug-2520-read-guard-hook-subprocess-env.test.cjs, which spawns
the hook with an env mirroring the actual Claude Code hook-subprocess
filter. Extend the legacy test harnesses to also strip the
propagation-verified CLAUDE_CODE_* vars so positive-path tests keep
passing when the suite itself runs inside a Claude Code session (same
class of leak as #2370 / PR #2375, now covering the new detection
signals).
Non-Claude-host behavior (OpenCode / MiniMax) is unchanged: with no
`session_id` on stdin and no CLAUDE_CODE_* env var, the advisory still
fires.
Closes#2520
* test(2520): isolate session_id signal from env fallbacks in regression test
Per reviewer feedback (Copilot + CodeRabbit on #2521): the session_id
isolation test used the helper's default CLAUDE_CODE_ENTRYPOINT /
CLAUDE_CODE_SSE_PORT values, so the env fallback would rescue the skip
even if the primary `data.session_id` check regressed. Pass an explicit
env override that clears those fallbacks, so only the stdin `session_id`
signal can trigger the skip.
Other cases (env-only fallback, negative / non-Claude host) already
override env appropriately.
---------
Co-authored-by: forfrossen <forfrossensvart@gmail.com>
