Stability checkpoint — Phase 2 complete + Phase 3 (O2+T2+DEMO1+DEMO2) + CI hygiene hardening

Phase 2 (UI) : OpenAPI→TS types (D1), axe-core a11y (T1), guided tour (DEMO3)
Phase 2 (svc): cosign re-verify (S1), Grafana exemplars→Tempo (O1), jqwik
               parallelism (T3), Hurl smoke collection (D3), ADR supersession
               graph (DOC3)

Phase 3 (svc): PrometheusRule + 6 runbooks + ADR-0048 + promtool CI (O2),
               k6 nightly load test (T2)
Phase 3 (UI) : /find-the-bug interactive (DEMO1), /incident-anatomy
               scripted walkthrough (DEMO2)

CI hygiene: k8s-apply + k8s-apply-prom shields (Docker VM cap, revisit
            2026-05-21), openapi-lint agents disabled + 600s budget,
            promtool-check-rules validates alert YAML.

New CLAUDE.md rules: file length hygiene (≥1000 split plan, ≥1500 split
now), Docker cleanup 4 triggers, subdirectory threshold tightened 10/15.

MRs merged: !128 (34 commits), !67 (24 commits). Both post-merge main
pipelines green on #615 (svc) + #322 (UI).