feat(smoke): joint-smoke mode against deployed flex-auth (assist FLEX-WP-0007 T4)

flex-auth asked ops-warden to help close FLEX-WP-0007 T4 (joint OpenBao + policy-gate
production smoke) against their deployed runtime (reachable on CoulombCore via the
flex-auth-coulombcore tunnel at 127.0.0.1:18090). The smoke previously spawned its own
local flex-auth, so it never exercised the deployed runtime.

Add FLEX_AUTH_EXTERNAL=1 to scripts/policy_gate_production_smoke.sh: skip the local
serve/load-registry and run the allow/deny/vault paths against the already-running
flex-auth, with a /healthz precheck that fails fast with a tunnel-up hint. Verified the
committed production_registry_snapshot.json is current vs inventory (4 actors). Recorded
in ADHOC-2026-06-29.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

workplans/ADHOC-2026-06-29.md

@@ -0,0 +1,38 @@
+---
+id: ADHOC-2026-06-29
+type: workplan
+title: "Ad Hoc Tasks — 2026-06-29"
+domain: infotech
+repo: ops-warden
+status: finished
+owner: claude
+topic_slug: custodian
+created: "2026-06-29"
+updated: "2026-06-29"
+---
+
+# Ad Hoc Tasks — 2026-06-29
+
+### T01 — Joint-smoke mode for the deployed flex-auth (assist FLEX-WP-0007 T4)
+
+```task
+id: ADHOC-2026-06-29-T01
+status: done
+priority: medium
+```
+
+flex-auth (msg `ea00620b`) asked ops-warden to help close FLEX-WP-0007 T4 (joint OpenBao
++ policy-gate production smoke). Their deployed runtime is reachable on CoulombCore via
+the flex-auth-coulombcore tunnel at `127.0.0.1:18090`, but `policy_gate_production_smoke.sh`
+spawned its **own** local flex-auth binary — so it never exercised the deployed runtime.
+
+- [x] Added `FLEX_AUTH_EXTERNAL=1` mode to `scripts/policy_gate_production_smoke.sh`: skips
+      the local `serve`/`load-registry` and runs the allow/deny/vault paths against the
+      already-running deployed flex-auth, with a `/healthz` precheck that fails fast with a
+      "is the flex-auth-coulombcore tunnel up?" hint (verified: clean exit 2 when down).
+- [x] Verified the committed `production_registry_snapshot.json` is **current** (rebuilt
+      from `~/.config/warden/inventory.yaml`, diff-clean; 4 actors).
+- [x] Answered flex-auth's three questions and handed the operator the exact CoulombCore
+      runbook (see reply). Remaining T4 steps are operator-gated and cannot run from the
+      workstation: mint a scoped `VAULT_TOKEN` (ops-warden holds no standing token by
+      design), run the joint smoke on CoulombCore, then flip `policy.enabled: true`.