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

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

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+---
+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
+feature: core-eslint
+depends-on: [02-boot-assertions]
+blocks: [03-b-ast-aware-eslint-rules]
+---
+
+## Goal
+Stand up the custom ESLint rule plugin in `@repo/core-eslint` and ship three
+structural conformance rules that don't require cross-file AST analysis.
+Editor + CLI feedback fires in <1s.
+
+## Why
+Boot-time assertion catches drift in bound use cases, but cannot catch:
+- Features that exist on disk but have no manifest at all
+- Use-case files lacking a sibling test file
+- Manifest declaring required cores that aren't in `pnpm-workspace.yaml`
+
+Structural ESLint rules surface these in the editor, before code is even
+saved past lint-on-save.
+
+## Done when
+- Custom rule plugin exists at `packages/core-eslint/plugin.js`
+- Three rules registered: `conformance/feature-must-have-manifest`,
+  `conformance/usecase-must-have-test-file`,
+  `conformance/required-cores-installed`
+- Each rule has RuleTester tests with positive + negative cases
+- `base.js` registers the plugin and enables the rules
+- `pnpm lint` passes for the current monorepo state (rules tuned to today's
+  reality — see Out of scope)
+
+## In scope
+- Custom rule plugin module at `packages/core-eslint/plugin.js`
+- Rule modules in `packages/core-eslint/rules/*.js`
+- Manifest text parser (`_manifest-source.js`) — regex-based, sufficient for
+  literal `as const` manifests
+- Workspace.yaml reader (`_workspace.js`)
+- Rule integration into `base.js`
+- Tests for each rule using ESLint's RuleTester
+
+## Out of scope
+- Cross-file AST analysis rules (`no-undeclared-event-publish`,
+  `no-undeclared-audit`) — milestone iii.b
+- Enforcement on features that don't yet have a manifest — `feature-must-have-manifest`
+  ships as a WARNING today (only auth has a manifest); flips to ERROR after
+  blog/media/navigation/marketing-pages get manifests
+- Manifest parser based on TypeScript compiler API — regex is sufficient for
+  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