lib/deploy-commit.sh: a rejected `git commit` (pre-commit hook,
protected branch, signing failure) now exits 6 (loud stderr, distinct
from rc 1's "nothing to do") instead of sharing rc 1 with the no-op
cases. Header comment documents the full 0/1/2/3/4/5/6 taxonomy.
Closes J4-22 (UNTESTABLE): at client repos, a failed deploy-state
commit was indistinguishable BY EXIT CODE from "nothing to do" (rc 1
was shared 3 ways); exit-code-only callers couldn't disambiguate
(stderr-parsing callers already could).
Caller census (per report's explicit gate): skills/deploy/SKILL.md
documents and parses this exit-code contract in TWO places (bootstrap
commit + incident-recovery commit). Flagged to the user before
committing; confirmed GO to add rc 6 there too (additive — no existing
code's meaning changes) so the documented contract stays accurate for
live deploy runs.
New T10 in lib/tests/deploy-commit.test.sh (+3 assertions, 13→16):
rejecting pre-commit hook sandbox — asserts rc 6, empty stdout (no
stale hash), HEAD unmoved.
GREEN: full `make test` exit 0 (deploy-commit 16/16 incl. T10).
shellcheck clean, bash -n clean.
Bastien Chanot
91c7dccdfb