build: address review on the pre-push hook and hooks-dir resolution

resolveGitHooksDir now returns a directory only when it is the repo's own
<git-common-dir>/hooks (compared on canonical paths), so a core.hooksPath
elsewhere, global or repo-local, is never written to by postinstall, while a
core.hooksPath pointing back at the repo's own .git/hooks still resolves.

The pre-push hook skips with a one-line notice when a pushed ref is not the
checked-out HEAD (tags peeled) or when git status shows uncommitted or
untracked changes under a path the checks read (src, config, scripts, test,
package.json, package-lock.json, install.sh), since the checks read the
working tree rather than the pushed commit.

Also: honest timing (~10-40s instead of ~15s), CLAUDE.md Session Safety note
on CODEMAN_SKIP_PREPUSH for another session's WIP, 14 (not 9) Playwright
tests, and a note that the browser-excludes check only sees direct imports.

scripts/check-browser-test-excludes.mjs

@@ -19,6 +19,9 @@
  *    (`inline-rename`, `opencode-resize`, `webgl-fallback`,
  *    `terminal-copy-shortcut`, `codex-predictive-echo`). What actually makes a
  *    file dangerous is importing a browser driver, so that is what is tested.
+ *    ⚠️ Only a DIRECT import is seen: a test that reaches playwright through a
+ *    helper module (e.g. `test/mobile/helpers/browser.ts`) is not detected, so
+ *    such a test still has to be added to `BROWSER_TEST_GLOBS` by hand.
  *
  * 2. **The exclusion side is answered by vitest itself**, via
  *    `vitest list --filesOnly`, rather than by re-implementing glob matching