refactor(work): move epic folders into docs/work/epics/

The previous layout placed epic folders directly under docs/work/
alongside prds/ and _system/. Tightening: epics now live in their
own docs/work/epics/ subfolder, peer to prds/ and _system/. Same
shape as the existing prds/ bucket.

Final docs/work/ layout:
  README.md
  prds/<slug>.prd.md
  _system/_state.json
  epics/<slug>/_epic.md + <story-folder>/_story.md

Renames (git mv preserves history):
- docs/work/binder-wrap-helper/
    -> docs/work/epics/binder-wrap-helper/
- docs/work/library-evaluation-policy/
    -> docs/work/epics/library-evaluation-policy/
- docs/work/ci-security-and-supply-chain/
    -> docs/work/epics/ci-security-and-supply-chain/

Tooling updates:
- state-builder.mjs walks workRoot/epics/ directly; SKIP_FOLDERS
  obsoleted (no more sibling folders to filter out).
- dispatch.mjs's findNextTask, tickStoryBulletInEpic, and
  flipEpicDoneIfAllStoriesDone all join with "epics" segment.
- prd-ship.mjs's deriveShippingCommits walks workRoot/epics/ and
  git-logs docs/work/epics/<epic>/.
- decomposer.prompt.md emits epics under docs/work/epics/<epic-id>/.
- handoff + grill-with-docs glossary references updated.
- Glossary entry for Epic updated.

Reserved future shape: when a task-tracker integration (ClickUp,
Linear) ships, the epics/ subfolder hosts <task-id>-<slug>/
folders. Today it just hosts bare slugs.

docs/glossary.md

@@ -273,7 +273,7 @@ The top-level requirements doc at `docs/work/prds/<date>-<slug>.prd.md`. Status
 _Avoid:_ spec (in this template the **ADR** is the durable design record; PRDs are the implementation seed).
 
 **Epic**:
-A large body of work, one folder under `docs/work/<epic-slug>/` with `_epic.md`. Decomposed from a PRD.
+A large body of work, one folder under `docs/work/epics/<epic-slug>/` with `_epic.md`. Decomposed from a PRD.
 
 **Story**:
 One use case or one technical capability, one folder under `<epic>/<story-slug>/` with `_story.md`. Type metadata: `user-story` or `technical-story`.

docs/work/_system/_state.json

@@ -1,5 +1,5 @@
 {
-  "updated_at": "2026-05-14T19:16:53.146Z",
+  "updated_at": "2026-05-14T19:21:52.736Z",
   "epics": {
     "binder-wrap-helper": {
       "status": "done",

docs/work/epics/binder-wrap-helper/01-wire-use-case-helper/_story.md

@@ -8,7 +8,7 @@ feature: core-shared
 depends-on: []
 blocks: [02-migrate-feature-binders, 03-update-generator-templates]
 created: 2026-05-13T19:17:10+02:00
-updated: 2026-05-14T19:16:52.691Z
+updated: 2026-05-14T19:21:52.308Z
 ---
 
 ## Goal

docs/work/epics/binder-wrap-helper/02-migrate-feature-binders/_story.md

@@ -8,7 +8,7 @@ feature: auth, blog, media, marketing-pages, navigation
 depends-on: [01-wire-use-case-helper]
 blocks: []
 created: 2026-05-13T19:17:10+02:00
-updated: 2026-05-14T19:16:52.691Z
+updated: 2026-05-14T19:21:52.308Z
 ---
 
 ## Goal

docs/work/epics/binder-wrap-helper/03-update-generator-templates/_story.md

@@ -8,7 +8,7 @@ feature: core-shared
 depends-on: [01-wire-use-case-helper]
 blocks: []
 created: 2026-05-13T19:17:10+02:00
-updated: 2026-05-14T19:16:52.691Z
+updated: 2026-05-14T19:21:52.308Z
 ---
 
 ## Goal

docs/work/epics/binder-wrap-helper/_epic.md

@@ -6,7 +6,7 @@ type: epic
 status: done
 features: [core-shared, auth, blog, media, marketing-pages, navigation]
 created: 2026-05-13T00:00:00Z
-updated: 2026-05-14T19:16:52.691Z
+updated: 2026-05-14T19:21:52.308Z
 ---
 
 ## Goal

docs/work/epics/ci-security-and-supply-chain/01-trace-schema-extensions/_story.md

@@ -13,7 +13,7 @@ blocks:
     05-trace-revalidation-workflow,
   ]
 created: 2026-05-14T18:59:12+02:00
-updated: 2026-05-14T19:16:52.691Z
+updated: 2026-05-14T19:21:52.308Z
 ---
 
 ## Goal

docs/work/epics/ci-security-and-supply-chain/02-socket-integration/_story.md

@@ -8,7 +8,7 @@ feature: tooling
 depends-on: [01-trace-schema-extensions]
 blocks: [08-reviewer-prompt-update]
 created: 2026-05-14T18:59:12+02:00
-updated: 2026-05-14T19:16:52.691Z
+updated: 2026-05-14T19:21:52.308Z
 ---
 
 ## Goal

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

@@ -8,7 +8,7 @@ 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
+updated: 2026-05-14T19:21:52.308Z
 ---
 
 ## Goal

docs/work/epics/ci-security-and-supply-chain/04-major-bump-reevaluation/_story.md

@@ -8,7 +8,7 @@ feature: scripts
 depends-on: [01-trace-schema-extensions]
 blocks: [05-trace-revalidation-workflow]
 created: 2026-05-14T18:59:12+02:00
-updated: 2026-05-14T19:16:52.691Z
+updated: 2026-05-14T19:21:52.308Z
 ---
 
 ## Goal

docs/work/epics/ci-security-and-supply-chain/05-trace-revalidation-workflow/_story.md

@@ -8,7 +8,7 @@ feature: scripts
 depends-on: [01-trace-schema-extensions, 04-major-bump-reevaluation]
 blocks: [09-ci-security-guide-and-docs]
 created: 2026-05-14T18:59:12+02:00
-updated: 2026-05-14T19:16:52.691Z
+updated: 2026-05-14T19:21:52.308Z
 ---
 
 ## Goal

docs/work/epics/ci-security-and-supply-chain/06-codeql-and-audit-signatures/_story.md

@@ -8,7 +8,7 @@ feature: tooling
 depends-on: []
 blocks: [08-reviewer-prompt-update]
 created: 2026-05-14T18:59:12+02:00
-updated: 2026-05-14T19:16:52.691Z
+updated: 2026-05-14T19:21:52.308Z
 ---
 
 ## Goal

docs/work/epics/ci-security-and-supply-chain/07-gitleaks-precommit/_story.md

@@ -8,7 +8,7 @@ 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
+updated: 2026-05-14T19:21:52.308Z
 ---
 
 ## Goal

docs/work/epics/ci-security-and-supply-chain/08-reviewer-prompt-update/_story.md

@@ -8,7 +8,7 @@ feature: tooling
 depends-on: [02-socket-integration, 06-codeql-and-audit-signatures]
 blocks: [09-ci-security-guide-and-docs]
 created: 2026-05-14T18:59:12+02:00
-updated: 2026-05-14T19:16:52.691Z
+updated: 2026-05-14T19:21:52.308Z
 ---
 
 ## Goal

docs/work/epics/ci-security-and-supply-chain/09-ci-security-guide-and-docs/_story.md

@@ -18,7 +18,7 @@ depends-on:
   ]
 blocks: []
 created: 2026-05-14T18:59:12+02:00
-updated: 2026-05-14T19:16:52.691Z
+updated: 2026-05-14T19:21:52.308Z
 ---
 
 ## Goal

docs/work/epics/ci-security-and-supply-chain/_epic.md

@@ -6,7 +6,7 @@ type: epic
 status: done
 features: [scripts, tooling, docs]
 created: 2026-05-14T00:00:00Z
-updated: 2026-05-14T19:16:52.691Z
+updated: 2026-05-14T19:21:52.308Z
 ---
 
 ## Goal

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

@@ -14,7 +14,7 @@ blocks:
     08-backfill-traces,
   ]
 created: 2026-05-14T06:52:02+02:00
-updated: 2026-05-14T19:16:52.691Z
+updated: 2026-05-14T19:21:52.308Z
 ---
 
 ## Goal

docs/work/epics/library-evaluation-policy/02-pre-commit-check-script/_story.md

@@ -8,7 +8,7 @@ feature: scripts
 depends-on: [01-trace-schema-foundation]
 blocks: [06-sandcastle-reviewer-prompt]
 created: 2026-05-14T06:52:02+02:00
-updated: 2026-05-14T19:16:52.691Z
+updated: 2026-05-14T19:21:52.308Z
 ---
 
 ## Goal

docs/work/epics/library-evaluation-policy/03-claude-hooks/_story.md

@@ -8,7 +8,7 @@ feature: tooling
 depends-on: []
 blocks: []
 created: 2026-05-14T06:52:02+02:00
-updated: 2026-05-14T19:16:52.691Z
+updated: 2026-05-14T19:21:52.308Z
 ---
 
 ## Goal

docs/work/epics/library-evaluation-policy/04-evaluate-library-skill/_story.md

@@ -8,7 +8,7 @@ feature: tooling
 depends-on: [01-trace-schema-foundation]
 blocks: [05-human-guide]
 created: 2026-05-14T06:52:02+02:00
-updated: 2026-05-14T19:16:52.691Z
+updated: 2026-05-14T19:21:52.308Z
 ---
 
 ## Goal

docs/work/epics/library-evaluation-policy/05-human-guide/_story.md

@@ -8,7 +8,7 @@ feature: docs
 depends-on: [04-evaluate-library-skill]
 blocks: [09-claude-md-update]
 created: 2026-05-14T06:52:02+02:00
-updated: 2026-05-14T19:16:52.691Z
+updated: 2026-05-14T19:21:52.308Z
 ---
 
 ## Goal

docs/work/epics/library-evaluation-policy/06-sandcastle-reviewer-prompt/_story.md

@@ -8,7 +8,7 @@ feature: tooling
 depends-on: [02-pre-commit-check-script]
 blocks: []
 created: 2026-05-14T06:52:02+02:00
-updated: 2026-05-14T19:16:52.691Z
+updated: 2026-05-14T19:21:52.308Z
 ---
 
 ## Goal

docs/work/epics/library-evaluation-policy/07-generator-pre-shipped-traces/_story.md

@@ -8,7 +8,7 @@ feature: tooling
 depends-on: [01-trace-schema-foundation]
 blocks: []
 created: 2026-05-14T06:52:02+02:00
-updated: 2026-05-14T19:16:52.691Z
+updated: 2026-05-14T19:21:52.308Z
 ---
 
 ## Goal

docs/work/epics/library-evaluation-policy/08-backfill-traces/_story.md

@@ -8,7 +8,7 @@ feature: docs
 depends-on: [01-trace-schema-foundation]
 blocks: []
 created: 2026-05-14T06:52:02+02:00
-updated: 2026-05-14T19:16:52.691Z
+updated: 2026-05-14T19:21:52.308Z
 ---
 
 ## Goal

docs/work/epics/library-evaluation-policy/09-claude-md-update/_story.md

@@ -8,7 +8,7 @@ feature: docs
 depends-on: [05-human-guide]
 blocks: []
 created: 2026-05-14T06:52:02+02:00
-updated: 2026-05-14T19:16:52.691Z
+updated: 2026-05-14T19:21:52.308Z
 ---
 
 ## Goal

docs/work/epics/library-evaluation-policy/_epic.md

@@ -6,7 +6,7 @@ type: epic
 status: done
 features: [scripts, tooling, docs]
 created: 2026-05-14T00:00:00Z
-updated: 2026-05-14T19:16:52.691Z
+updated: 2026-05-14T19:21:52.308Z
 ---
 
 ## Goal