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/03-claude-hooks/_story.md

@@ -0,0 +1,44 @@
+---
+id: 03-claude-hooks
+epic: library-evaluation-policy
+title: Claude PreToolUse / PostToolUse hooks for library-policy nudge
+type: technical-story
+status: done
+feature: tooling
+depends-on: []
+blocks: []
+created: 2026-05-14T06:52:02+02:00
+updated: 2026-05-14T19:16:52.691Z
+---
+
+## Goal
+
+Write `.claude/hooks/library-policy-nudge.sh` — a single hook script that dispatches on `tool_use_type` to handle both `PreToolUse` (Bash invocations matching `pnpm add` / `pnpm i <pkg>`) and `PostToolUse` (Edit/Write on any `**/package.json`). On match, emit a non-blocking system-reminder pointing the agent at the `evaluate-library` skill with the exact invocation pattern. Register the hook in `.claude/settings.json` following the same pattern as `generator-first-nudge.sh`.
+
+## Why
+
+Agents (and developers) running `pnpm add` by reflex bypass the policy before the pre-commit gate fires. The PreToolUse hook injects the skill reminder _before_ the install runs — the cheapest possible intervention point. The PostToolUse hook catches the rarer case where an agent edits `package.json` directly without running the install command.
+
+## Done when
+
+- `.claude/hooks/library-policy-nudge.sh` exists, is executable, dispatches on `CLAUDE_TOOL_USE_TYPE` (or equivalent hook env var), and emits the reminder to stdout when a `pnpm add`/`pnpm i <pkg>` bash command is detected or when an Edit/Write tool targets a path matching `**/package.json`.
+- The hook is registered in `.claude/settings.json` (or `.claude/settings.local.json` if per-repo convention) under both `PreToolUse` and `PostToolUse` event types, matching the registration pattern of `generator-first-nudge.sh`.
+- The reminder text includes the literal string `/evaluate-library` and the argument template `<name> --tier <feature|core|app> --target <package-path>` so the agent sees the exact invocation.
+- Bash smoke tests (same style as any existing hook tests): pipe a mocked Claude hook payload `{ "tool_input": { "command": "pnpm add foo" } }` into the script and assert stdout contains the skill-reminder marker; pipe a payload for `pnpm add -D foo` (devdep) and assert no reminder emitted; pipe an Edit payload on `src/feature.manifest.ts` and assert no reminder emitted.
+- `pnpm lint && pnpm fallow:audit` pass.
+
+## In scope
+
+- `.claude/hooks/library-policy-nudge.sh` — the hook script.
+- `.claude/settings.json` (or equivalent) — hook registration lines.
+- Bash smoke tests for the hook script.
+
+## Out of scope
+
+- Hook auto-deny or blocking behavior — the hook is advisory only (non-blocking system-reminder).
+- Hooks for `npm install` / `yarn add` — the repo is pnpm-only.
+- Integration with the skill implementation (Story 04) — the hook emits a text reminder; the skill is a separate file.
+
+## Tasks
+
+- [x] Investigate how `generator-first-nudge.sh` is registered (read `.claude/settings.json` and the existing hook script) to confirm the env-var names, payload shape, and registration keys; then write `.claude/hooks/library-policy-nudge.sh` + register it in the settings file + write bash smoke tests covering `pnpm add <pkg>` (reminder), `pnpm add -D <pkg>` (no reminder), Edit on non-package.json (no reminder), Edit on `package.json` (reminder); all gates pass on this single commit.