refactor(work): drop date prefixes + move _state.json into _system/

Convention shift: epic folders + PRD filenames + frontmatter id
fields are now bare slugs. The created: timestamp (Phase 2) carries
the date; folder names don't repeat it. A future <task-id>-<slug>
shape (e.g. ClickUp) lands cleanly when that integration ships.

Renames (git mv preserves history):
- docs/work/2026-05-13-binder-wrap-helper/
    -> docs/work/binder-wrap-helper/
- docs/work/2026-05-14-library-evaluation-policy/
    -> docs/work/library-evaluation-policy/
- docs/work/2026-05-14-ci-security-and-supply-chain/
    -> docs/work/ci-security-and-supply-chain/
- docs/work/prds/2026-05-13-binder-wrap-helper.prd.md
    -> docs/work/prds/binder-wrap-helper.prd.md
- docs/work/prds/2026-05-13-coverage-architecture.prd.md
    -> docs/work/prds/coverage-architecture.prd.md
- docs/work/prds/2026-05-14-library-evaluation-policy.prd.md
    -> docs/work/prds/library-evaluation-policy.prd.md
- docs/work/prds/2026-05-14-ci-security-and-supply-chain.prd.md
    -> docs/work/prds/ci-security-and-supply-chain.prd.md

Frontmatter updates inside the renamed files: epic id, epic prd,
story epic, PRD id, PRD builds-on all drop date prefixes.

System folder + state file move:
- New docs/work/_system/ holds framework-managed state.
- docs/work/_state.json -> docs/work/_system/_state.json.
- state-builder.mjs adds _system to SKIP_FOLDERS.
- cli.mjs + state-sync-guard.mjs + .husky/pre-commit point at the
  new path.

template-reset-v1 epic deleted entirely (one-off cleanup epic from
the pre-date-convention era; status was already done).

Generator-template updates (so new artifacts ship in the right
shape):
- .sandcastle/decomposer.prompt.md emits bare-slug folder names +
  ISO created: timestamp.
- .claude/skills/to-prd/SKILL.md template uses bare-slug filename +
  bare-slug id field + ISO created: timestamp.

Doc reference updates: glossary, runbook, agent-first-workflow-
and-conformance, reviewer prompt, ADR-020, ADR-022, ADR-023 all
point at the new paths/slugs.

docs/work/ci-security-and-supply-chain/03-renovate-adoption/_story.md

@@ -0,0 +1,42 @@
+---
+id: 03-renovate-adoption
+epic: ci-security-and-supply-chain
+title: Renovate adoption
+type: technical-story
+status: done
+feature: tooling
+depends-on: []
+blocks: [09-ci-security-guide-and-docs]
+created: 2026-05-14T18:59:12+02:00
+updated: 2026-05-14T19:16:52.691Z
+---
+
+## Goal
+
+Ship `.github/renovate.json` configuring automated dependency management: grouped per-ecosystem npm bumps, Dockerfile base-image tracking, GitHub Actions SHA pinning, automerge for green minor+patch PRs, and a single dependency dashboard issue.
+
+## Why
+
+Major-tag pinning for GitHub Actions is documented insecure — the 2025 `tj-actions/changed-files` incident proved it. Renovate's `pinGitHubActionDigests` preset automates the one-time SHA-pin sweep and keeps SHAs current thereafter. Grouping ecosystem clusters (Sentry, OTel, tRPC, Payload, Inversify) into weekly PRs prevents noise while ensuring drift is surfaced. Automerge on green minor+patch PRs removes human toil for routine bumps.
+
+## Done when
+
+- `.github/renovate.json` exists and is valid JSON, extending presets: `config:base`, `helpers:pinGitHubActionDigests`, `:separateMajorReleases`, `:automergeMinor`, `:automergePatch`.
+- `packageRules` groups `@sentry/*`, `@opentelemetry/*`, `@trpc/*`, `payload*`, and `inversify*` into per-cluster weekly PRs.
+- Dockerfile manager is enabled for `.sandcastle/Dockerfile`.
+- `dependencyDashboard: true` is set (opens a single Renovate-managed issue summarising open + queued PRs, labeled `renovate/dashboard` per PRD Q6).
+- Renovate's bump commits use `chore(deps):` (minor/patch) and `chore(deps-major):` (major) commit-message prefixes so release-please's per-package bump rules apply cleanly.
+- `pnpm typecheck && pnpm lint && pnpm test && pnpm conformance && pnpm fallow:audit && pnpm coverage:diff` all pass (no executable code change; JSON config only).
+
+## In scope
+
+- `.github/renovate.json` — full Renovate configuration.
+
+## Out of scope
+
+- Verifying the first Renovate PR (SHA-pin sweep) — that happens when the GitHub App runs, not at commit time. The success criterion (all `@v<N>` pins rewritten to SHAs) is verified when Renovate's first PR merges.
+- Renovate Dependency Dashboard → `docs/work/` task integration — explicitly out of scope in the PRD.
+
+## Tasks
+
+- [x] Create `.github/renovate.json` extending presets `config:base`, `helpers:pinGitHubActionDigests`, `:separateMajorReleases`, `:automergeMinor`, `:automergePatch`; add `packageRules` grouping `@sentry/*`, `@opentelemetry/*`, `@trpc/*`, `payload*`, `inversify*` into weekly per-cluster PRs; enable Dockerfile manager for `.sandcastle/Dockerfile`; set `dependencyDashboard: true`; set `commitMessagePrefix` to enforce `chore(deps):` / `chore(deps-major):` per Conventional Commits; one commit, all gates pass.