Stability checkpoint — housekeeping batch : path fix + ADR regen + audit rotation

- **chore(stability-check): fix UI_DIR for new flat layout (post-2026-04-26 migration)** — script was hardcoded to `$SVC_DIR/../../js/mirador-ui` (pre-migration). Now tries the flat layout first (`$SVC_DIR/../mirador-ui`), falls back to the old workspace-modern path for backward compatibility.
- **chore(adr): regen flat index** — picked up ADR-0063 (order-line refund state machine), bringing the flat index to 63 ADRs.
- **chore(audit): rotate retention** — dropped `stability-2026-04-20-2358.md`, added `stability-2026-04-28-0447.md` (0 BLOCKING / 11 ATTENTION findings).

CI :
- ✅ Main pipeline #2483919691 green at 2026-04-28 05:02 — https://gitlab.com/mirador1/mirador-service-java/-/pipelines/2483919691
- ✅ MR pipeline (chore/stability-housekeeping !248) green, merged 2026-04-28 05:02

Local test pass :
- ⏭ `./mvnw verify -q` — N/A this rev (chore-only, no code touched, runs in CI)
- ✅ `bin/dev/stability-check.sh` — completed end-to-end on the new flat layout, 0 BLOCKING findings ([report](docs/audit/stability-2026-04-28-0447.md))
- ✅ `infra/common/bin/dev/regen-adr-index.sh --in-place` — clean run, 63 ADRs accounted for

Regression check vs stable-v1.2.13 :
- ✅ All previous endpoints + tests preserved (chore commits don't touch code)
- ✅ MCP server : 14 tools wired, list still complete
- ✅ Phase B/C ONNX cross-language inference still working (no ML touched)

This is a **housekeeping** tag — same mastery profile as stable-v1.2.13. See [stable-v1.2.13](https://gitlab.com/mirador1/mirador-service-java/-/tags/stable-v1.2.13) annotation for the full themes breakdown across the 10 axes (IA / Sécurité / Fonctionnel / Infra Cloud / Observabilité / Qualité / CI-CD / Architecture / Frontend / DevX). Delta this rev :

- `bin/dev/stability-check.sh` resolves UI_DIR cleanly on the new `~/dev/mirador/` flat layout (post-2026-04-26 polyrepo consolidation)
- 5 GitHub mirrors caught up (Java/UI/Python/Common/Shared) — 90+ commits + 1 new tag pushed
- Lefthook re-installed on Java + UI (was missing pre-commit hooks)

- ADR flat index regenerated — drift detected by stability-check, ADR-0063 now indexed

- Today's stability report (`stability-2026-04-28-0447.md`) captured the post-tag state : 0 BLOCKING / 11 ATTENTION
- 6 ATTENTION items already cleared in this batch + adjacent commits (lefthook x2, ADR drift, mirror sync x5, README dead links)

- Same as stable-v1.2.13 (Spring AI 1.0.0-M6 GA migration pending, QualityReportEndpoint 1934 LOC split planned)
- **RTO/RPO measurement** : 🚫 still not measured. Documented in TASKS.md as deferred — needs Chaos Mesh deployed + DB pod accessible to execute. Not in scope for this rev.
- **Customer\* mini-domain rename** : ⚠️ 503 cross-repo references identified (Java 263 + Python 102 + UI 138). Spawned to a dedicated session per user authorization 2026-04-28 — execution ongoing in isolated worktree.

- Customer\* rename completion (in dedicated session)
- Spring AI 1.0.0 GA migration (when ready)
- Phase F : Customer Churn ConfigMap promotion to dev cluster