feat(api): capability enforcement on writes

Add lib/api/cap.js: requireWrite(entity_type) maps HTTP method to
action, runs canAct, and tags req.capTier as allow|suggest|deny→403.
Mutating routes (pages, projects, tasks, refs, resources, source_docs)
now check req.capTier and either run the repo (allow) or divert to
pending_changes returning 202 (suggest). Owner and worker actors stay
on the allow path. requireOwner helper added for Task 11.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

lib/api/routes/source_docs.js

@@ -3,6 +3,7 @@ import { z } from 'zod';
 import * as repo from '../../db/repos/source_docs.js';
 import { validate } from '../validate.js';
 import { NotFoundError, ValidationError, asyncWrap } from '../errors.js';
+import { requireWrite, divertToPending } from '../cap.js';
 
 const baseFields = {
   name: z.string().min(1).max(200),
@@ -28,10 +29,15 @@ export const router = Router();
 export const resourcesScopedRouter = Router({ mergeParams: true });
 
 resourcesScopedRouter.post('/',
+  requireWrite('source_doc'),
   validate({ params: resourceParams, body: createSchema }),
   asyncWrap(async (req, res) => {
+    const payload = { ...req.body, resource_id: req.params.resource_id };
+    if (req.capTier === 'suggest') {
+      return divertToPending(req, res, { entity_type: 'source_doc', action: 'create', payload });
+    }
     try {
-      const row = await repo.create({ ...req.body, resource_id: req.params.resource_id }, req.actor);
+      const row = await repo.create(payload, req.actor);
       res.status(201).json(row);
     } catch (e) {
       if (e.code === '23503') throw new ValidationError('invalid resource', {
@@ -52,19 +58,31 @@ router.get('/:id',
 );
 
 router.patch('/:id',
+  requireWrite('source_doc'),
   validate({ params: idParams, body: patchSchema }),
   asyncWrap(async (req, res) => {
     const existing = await repo.getById(req.params.id);
     if (!existing) throw new NotFoundError('source doc not found');
+    if (req.capTier === 'suggest') {
+      return divertToPending(req, res, {
+        entity_type: 'source_doc', entity_id: req.params.id, action: 'update', payload: req.body
+      });
+    }
     res.json(await repo.update(req.params.id, req.body, req.actor));
   })
 );
 
 router.delete('/:id',
+  requireWrite('source_doc'),
   validate({ params: idParams }),
   asyncWrap(async (req, res) => {
     const existing = await repo.getById(req.params.id);
     if (!existing) throw new NotFoundError('source doc not found');
+    if (req.capTier === 'suggest') {
+      return divertToPending(req, res, {
+        entity_type: 'source_doc', entity_id: req.params.id, action: 'delete', payload: {}
+      });
+    }
     await repo.del(req.params.id, req.actor);
     res.status(204).end();
   })