docs(work): close story 03.a — structural ESLint rules

docs/work/conformance-system-v1/03-a-structural-eslint-rules/_story.md

@@ -3,7 +3,7 @@ id: 03-a-structural-eslint-rules
 epic: conformance-system-v1
 title: Structural ESLint rules (feature-must-have-manifest, usecase-must-have-test-file, required-cores-installed)
 type: technical-story
-status: in-progress
+status: done
 feature: core-eslint
 depends-on: [02-boot-assertions]
 blocks: [03-b-ast-aware-eslint-rules]
@@ -52,13 +52,13 @@ saved past lint-on-save.
   literal manifests; the AST path comes in iii.b
 
 ## Tasks
-- [ ] Story 03.a scaffold
-- [ ] Manifest source helper (`_manifest-source.js`)
-- [ ] Workspace helper (`_workspace.js`)
-- [ ] `feature-must-have-manifest` rule + tests
-- [ ] `usecase-must-have-test-file` rule + tests
-- [ ] `required-cores-installed` rule + tests
-- [ ] Plugin module + `exports` entry in `package.json`
-- [ ] Wire plugin into `base.js`
-- [ ] Verify `pnpm lint` passes against the monorepo
-- [ ] Final verification + story closeout
+- [x] Story 03.a scaffold
+- [x] Manifest source helper (`_manifest-source.js`)
+- [x] Workspace helper (`_workspace.js`)
+- [x] `feature-must-have-manifest` rule + tests
+- [x] `usecase-must-have-test-file` rule + tests
+- [x] `required-cores-installed` rule + tests
+- [x] Plugin module + `exports` entry in `package.json`
+- [x] Wire plugin into `base.js`
+- [x] Verify `pnpm lint` passes against the monorepo
+- [x] Final verification + story closeout