job7 step C: gitleaks backstop — .gitleaks.toml, pre-commit hook, make scan-secrets

Pre-commit (lib/gitflow.sh emit-hook) now runs `gitleaks git --staged` right
after the root-commit/merge-in-progress guard, on ANY branch — not gated by
branch protection, since secrets shouldn't land anywhere. Non-blocking if
gitleaks isn't installed (warn + pass). gitleaks 8.30.1: `protect` isn't
listed in --help anymore (still runs, but undocumented) — used the
documented `git --staged` equivalent instead.

.gitleaks.toml allowlists the 3 false-positive classes from the job7 triage
(marketplace.json 40-hex "sha" fields, superpowers ws-protocol.test.js nonce,
git-game test-secret-* fixtures) plus a 4th entry for ~/.claude/.env itself —
not a false positive, but scanning our own canonical vault (BDR-026) is pure
noise for a tool meant to catch stray copies. All 4 verified empirically
against the real flagged files/values before being added, not assumed from
gitleaks' docs.

`make scan-secrets` scans this repo's git history + ~/.claude (dir scan),
redacted JSON to .audit/ (verified: --redact scrubs Match/Secret in the
report itself, not just console logs — safe to commit). Repo: 0 findings.
~/.claude: 18 remaining across 8 files — 5 match the known job7 triage
(pending the GO-gated purge in step D), 3 are new discoveries outside the
original triage scope (flagged for the user, not characterized further —
never read a flagged file's content past what gitleaks' redacted report
gives you).

lib/gitflow-test.sh T16: fake secret on a feature branch (not main/develop)
→ blocked, proving the check isn't gated by branch protection; clean commit
passes; PATH without gitleaks → warns and still commits. 96/96 green.

lib/gitflow.sh

@@ -221,6 +221,19 @@ br=\$(git symbolic-ref --short -q HEAD 2>/dev/null)
 git rev-parse --verify -q HEAD >/dev/null 2>&1 || exit 0   # root commit — allow
 [ -f "\$gd/MERGE_HEAD" ] && exit 0                          # merge in progress — allow
 
+# Secret backstop (job7) — any branch, not just protected ones. Non-blocking
+# if gitleaks isn't installed; auto-discovers ./.gitleaks.toml (repo root).
+if command -v gitleaks >/dev/null 2>&1; then
+  if ! gitleaks git --staged --no-banner >/dev/null 2>&1; then
+    echo "gitflow pre-commit: BLOCKED — gitleaks found a secret in staged changes." >&2
+    echo "  Details: gitleaks git --staged --no-banner" >&2
+    echo "  Genuine false-positive? add an allowlist rule to .gitleaks.toml — never bypass with --no-verify." >&2
+    exit 1
+  fi
+else
+  echo "gitflow pre-commit: gitleaks not installed — secret scan skipped (https://github.com/gitleaks/gitleaks)." >&2
+fi
+
 case "\$br" in
   $GITFLOW_MAIN|$GITFLOW_DEVELOP) ;;                        # protected — keep checking
   *) exit 0 ;;                                              # working branch — allow