docs: warn agents a slow git push is the pre-push hook, not a network hang

[zigrivers]

Summary

Adds a note in CLAUDE.md (Committing and Creating PRs) and
docs/git-workflow.md (Local Hooks) so future AI agents don't misdiagnose a
slow git push as a network/auth/HTTP-2 failure.

Why: make hooks installs a pre-push hook that runs the full bats/test
suite (several minutes) before the upload, with little output. Because the repo
is public, git fetch/ls-remote need no auth and return instantly — so a slow
push can look network-specific when it's just the hook. The note explains how to
confirm with GIT_TRACE=1 git push and to use git push --no-verify only when
make check-all already passed on the exact commit.

Docs-only. Verified by pushing this branch with the hook enabled — it ran the
full bats suite (85/85 ok) and completed normally.

Test Plan

• Pre-push hook ran green on push (85/85 bats)
• CI check job passes