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/library-evaluation-policy/01-trace-schema-foundation/_story.md

@@ -0,0 +1,51 @@
+---
+id: 01-trace-schema-foundation
+epic: library-evaluation-policy
+title: Trace schema module + docs/library-decisions/ foundation
+type: technical-story
+status: done
+feature: scripts
+depends-on: []
+blocks:
+  [
+    02-pre-commit-check-script,
+    04-evaluate-library-skill,
+    07-generator-pre-shipped-traces,
+    08-backfill-traces,
+  ]
+created: 2026-05-14T06:52:02+02:00
+updated: 2026-05-14T19:16:52.691Z
+---
+
+## Goal
+
+Create the shared Zod-validated trace-schema module (`scripts/library-decisions/schema.mjs`) that every enforcement layer imports, and establish `docs/library-decisions/` with a `_template.md` schema reference that documents the required frontmatter + heading shape for all future traces.
+
+## Why
+
+All four enforcement layers (skill, pre-commit check, generator templates, sandcastle reviewer) need a single authoritative definition of what a valid library trace looks like. Without a shared module, each layer would re-implement the parse/validate logic independently and drift. The `_template.md` gives human contributors and agents a copy-pasteable starting point.
+
+## Done when
+
+- `scripts/library-decisions/schema.mjs` exists and exports: (1) a Zod schema validating the full trace frontmatter (all fields from ADR-022 §4 including nested `filter-results` object), (2) a `parseTrace(filePath)` function that reads + validates a `.md` file's frontmatter, (3) a `validateTrace(raw)` function for validating already-parsed objects.
+- `scripts/library-decisions/schema.test.mjs` covers: valid trace round-trips without error; missing required field throws; unknown filter key rejected; invalid enum value rejected; `accepted-cves` optional field accepted.
+- `docs/library-decisions/_template.md` exists with the complete frontmatter schema (all fields, all enums documented) and all required section headings (`## Filter: <name>` × 8 + `## Prompt: <name>` × 3) in the machine-checkable order from ADR-022.
+- `docs/library-decisions/` directory is committed (can be just `_template.md` + `.gitkeep` if no traces yet).
+- `pnpm typecheck && pnpm lint && pnpm test && pnpm conformance && pnpm fallow:audit && pnpm coverage:diff` all pass.
+
+## In scope
+
+- `scripts/library-decisions/schema.mjs` — Zod schema + parse/validate exports.
+- `scripts/library-decisions/schema.test.mjs` — unit tests (vitest or node:test; match the pattern used by `scripts/work/` tests).
+- `docs/library-decisions/_template.md` — schema reference document.
+
+## Out of scope
+
+- The pre-commit check script (`check.mjs`) — Story 02.
+- The skill itself — Story 04.
+- Actual trace files (backfill) — Story 08.
+- Generator template changes — Story 07.
+
+## Tasks
+
+- [x] Create `scripts/library-decisions/schema.mjs` with Zod frontmatter schema (all fields from ADR-022 §4: `package`, `version`, `tier`, `decision`, `date`, `deciders`, `adr`, `filter-results` nested object with all 8 filter keys and their enum values, `verification-commands`, `accepted-cves` optional), plus `parseTrace(filePath)` and `validateTrace(raw)` exports; write `schema.test.mjs` covering valid round-trip, missing-field rejection, invalid-enum rejection, and optional `accepted-cves`; create `docs/library-decisions/_template.md` with full frontmatter schema + all 11 required headings in ADR-022 order; all gates pass on this single commit.