feat: plan 16 P1 (SEC-08/09/19/20/21) — fail-open/DoS/authz hardening

- SEC-08 pii-mask: fail-closed on missing rules / broken regex (no unmasked leak)
- SEC-09: input-size cap + fail-closed reads (security-check/drift-detect/context-compress); non-UTF8 no longer crashes
- SEC-19: control-plane store POSIX flock + atomic tmp+rename write
- SEC-20: new toolchain-verify.sh (missing/PATH-shadowed/in-workspace binary -> refuse); wired into harness-preflight
- SEC-21: model-call timeout 180->60s configurable + per-run call budget
- SEC-11 realized by SEC-17 prod profile (no code)
- 5 fail-able test suites wired into ci-harness-gate.sh; test-integrity manifest regenerated

Verify: SEC+integrity gate 16/0, run-casan4 0-FAIL, adversarial 44/44, no regressions.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

AINative_OKR_CASAN5/.specify/scripts/bash/ci-harness-gate.sh

@@ -96,6 +96,12 @@ run "phase-sec06-cp-signed"     bash "$TESTS/phase-sec06-tests.sh"
 run "phase-sec16-bundle"        bash "$TESTS/phase-sec16-tests.sh"
 run "phase-sec17-prod-profile"  bash "$TESTS/phase-sec17-tests.sh"
 run "phase-sec18-test-integrity" bash "$TESTS/phase-sec18-tests.sh"
+# Plan-16 P1 (authz / fail-open / DoS)
+run "phase-sec08-pii-failclosed" bash "$TESTS/phase-sec08-tests.sh"
+run "phase-sec09-input-caps"     bash "$TESTS/phase-sec09-tests.sh"
+run "phase-sec19-atomic-store"   bash "$TESTS/phase-sec19-tests.sh"
+run "phase-sec20-toolchain"      bash "$TESTS/phase-sec20-tests.sh"
+run "phase-sec21-model-budget"   bash "$TESTS/phase-sec21-tests.sh"
 
 # ARCH-02: coverage cannot silently drop; ARCH-01: harness/policy cannot silently
 # drift. Both SKIP cleanly when no manifest is provisioned (non-strict dev/CI).