feat(c7): incident response — severity classifier + scoped kill-switch + runbook (V23)

Closes the last fully-[planned] Track-C dimension (was scored 1).
- incident.sh raise <event>: classify severity via incident-severity.map
  (LOW/MED/HIGH/CRIT), record a structured entry (owner routing), and for
  HIGH/CRIT auto-engage the scoped kill-switch + dispatch an alert (reuses H6
  alert-dispatch.sh). Exit 2 on HIGH/CRIT so a pipeline gate goes red.
- kill-switch.sh engage/clear/check/status, scoped by project/model/provider
  (+ global). `check` exits 2 when engaged so gates honor it.
- casan-harness.sh honors an engaged kill-switch before running (opt-in
  CASAN_KILLSWITCH_ENFORCE=1, default OFF → baseline unchanged).
- incident-runbook.md: severity→owner→response + postmortem template + prod TODO.
- phase-c7-incident-tests.sh: 15 checks — severity grading, auto kill-switch on
  HIGH/CRIT, MED-only records, lifecycle, global scope, structured record, and
  the production wrapper refusing to run under an engaged switch.

Baselines: run-casan4 35/35, adversarial 44/44. New suite total: 175 → 190.

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

AINative_OKR_CASAN5/.specify/security/incident-severity.map

@@ -0,0 +1,17 @@
+# CASAN — Incident severity map (C7 / V23). Line format: <event-type> <severity>
+# severity ∈ LOW | MED | HIGH | CRIT. HIGH/CRIT auto-engage the kill-switch.
+# Mirrors the Plan-07 C0 severity table.
+secret-to-cloud         CRIT
+tool-write-sensitive    CRIT
+private-key-exposure     CRIT
+dependency-postinstall  HIGH
+dependency-malicious    HIGH
+audit-chain-broken      HIGH
+telemetry-tamper        HIGH
+sandbox-escape          HIGH
+evidence-pack-tampered  HIGH
+cost-budget-exceeded    MED
+benign-fp-exceeded      MED
+drift-detected          MED
+approval-forged         HIGH
+default                 MED