feat(task-013): add draft assembly API, immutable versioning, and editor preview

tasks/013-draft-assembly-editor-preview.md

@@ -35,13 +35,13 @@ Development description: Assemble section scaffolds into a canonical Markdown/MD
 
 ## Acceptance Criteria
 
-- [ ] TDD pre-requirement: before implementation, write one failing behavior test that assembles a draft from successful section scaffolds through the public API; proceed one draft behavior at a time and record evidence in `Result`.
-- [ ] Draft assembly includes all planned sections in order.
-- [ ] Draft includes metadata, FAQ, visual placeholders, evidence references, and unsupported claim warnings.
-- [ ] Draft version 1 is immutable after approval-relevant edits; edits create a new version.
-- [ ] Generic Markdown/MDX preview renders headings, links, tables, images/placeholders, and FAQ.
-- [ ] Editor can compare or select draft versions.
-- [ ] Draft assembly fails clearly if required section scaffolds are missing.
+- [x] TDD pre-requirement: before implementation, write one failing behavior test that assembles a draft from successful section scaffolds through the public API; proceed one draft behavior at a time and record evidence in `Result`.
+- [x] Draft assembly includes all planned sections in order.
+- [x] Draft includes metadata, FAQ, visual placeholders, evidence references, and unsupported claim warnings.
+- [x] Draft version 1 is immutable after approval-relevant edits; edits create a new version.
+- [x] Generic Markdown/MDX preview renders headings, links, tables, images/placeholders, and FAQ.
+- [x] Editor can compare or select draft versions.
+- [x] Draft assembly fails clearly if required section scaffolds are missing.
 
 ## Verification
 
@@ -51,9 +51,31 @@ Development description: Assemble section scaffolds into a canonical Markdown/MD
 
 ## Result
 
-- Status: Pending execution.
-- TDD plan: To be filled during execution.
-- Red evidence: To be filled during execution.
-- Green evidence: To be filled during execution.
-- Refactor notes: To be filled during execution.
-- Verification output: To be filled during execution.
+- Status: Completed. Pre-requirement (RED) and implementation (GREEN) finished.
+- TDD plan:
+  1. Keep the original RED pre-requirement behavior test for `POST /api/articles/{article_id}/draft/assemble`.
+  2. Extend backend integration coverage for draft assembly payload completeness, immutable versioning, missing scaffold conflict, unsupported warning propagation, and not-found paths.
+  3. Implement backend drafts application layer and public routes for assemble/list/get/patch.
+  4. Extend shared API contracts (OpenAPI + generated TS types).
+  5. Implement frontend draft editor with version selector, compare summary, and generic markdown preview parser/renderer.
+  6. Add frontend model tests for preview parsing and version comparison.
+- Red evidence:
+  - Pre-requirement test `apps/backend/tests/integration/test_draft_assembly_public_api.py::DraftAssemblyPublicApiTest::test_assemble_draft_from_successful_section_scaffolds` initially failed before implementation.
+  - Observed RED error before implementation: `AssertionError: 201 != 404 : {"detail":"Not Found"}`.
+- Green evidence:
+  - `POST /api/articles/{article_id}/draft/assemble` implemented and returns `201` with canonical draft payload.
+  - `GET /api/articles/{article_id}/drafts`, `GET /api/articles/{article_id}/drafts/{draft_id}`, and `PATCH /api/articles/{article_id}/drafts/{draft_id}` implemented and covered.
+  - Immutable versioning verified: patch creates `v2+`, base draft remains unchanged.
+  - Missing required successful section scaffolds returns clear `409`.
+  - Frontend generic preview parser renders headings, links, tables, images/placeholders, and FAQ blocks.
+  - Frontend editor supports version selection and compare summary.
+- Refactor notes:
+  - Added dedicated backend drafts service (`application/drafts.py`) and drafts route module to isolate draft logic from evidence/plan flows.
+  - Extended `article_drafts` persistence model with canonical body and metadata lists (`faq_items`, placeholders, evidence refs, warnings, based_on_draft_id`) for explicit version snapshots.
+- Verification output:
+  - `PYTHONPATH=/private/tmp/pupline-backend-deps python3 -m unittest apps/backend/tests/integration/test_draft_assembly_public_api.py` -> OK (5 tests)
+  - `PYTHONPATH=/private/tmp/pupline-backend-deps python3 -m unittest apps/backend/tests/integration/test_parallel_production_public_api.py` -> OK (6 tests)
+  - `PYTHONPATH=/private/tmp/pupline-backend-deps python3 -m unittest apps/backend/tests/integration/test_evidence_matrix_public_api.py` -> OK (2 tests)
+  - `node apps/frontend/tests/draft_editor.model.test.mjs` -> OK
+  - `node apps/frontend/tests/article_detail.model.test.mjs` -> OK
+  - `pnpm --dir apps/frontend typecheck` -> OK