Add hook smoke tests — 20 tests across all 10 hooks

[5uck1ess]

Summary

First-ever test coverage for the hook enforcement layer. 20 smoke tests across all 10 registered hooks, running as a new CI job.

What's tested

Hook	Tests	Key behaviors
safety-check.sh	3	Allow safe command, block rm -rf / (exit 2), empty input
audit-trail.sh	2	Log command, empty input
rtk-rewrite.sh	1	Pass through
pr-gate.sh	1	Allow git status
security-patterns.sh	2	Allow clean code, detect SQL concatenation
post-validate.sh	2	Clean output, empty input
slop-detect.sh	1	Allow clean code
lang-review.sh	4	Clean Go, error-path detection, skip non-code, empty input
subagent-stop.sh	2	Approve clean output, empty input
stop-gate.sh	2	Approve clean tree, empty input

CI

New hook-smoke-tests job runs in parallel with build-and-test and validate-counts.

Test plan

• All 20 tests pass locally
• CI passes with the new job