merge: AgentProject membership — the junction is now load-bearing

Merges feat/agent-project-membership (task 166/152). An agent can finally join
many projects: membership routes, per-membership role and optional brain
override, chat resolving context from the membership, and CLI attach-agent /
detach-agent / get memberships. The legacy Agent.projectId fallback is kept for
this release as the schema comment promises.

Conflict resolved in main.ts: that branch added its RBAC case to
mapUrlToPermission inline, while this branch had extracted the function to
middleware/url-permission.ts so it could be tested. Kept the extraction and
ported the case into it — joining a team is `edit:agents:<name>`, not
`create:agents`, which is the authority to mint a whole agent.

Also fixes something the extraction makes possible. security.test.ts contained a
hand-copied reproduction of mapUrlToPermission, because main.ts self-invokes
main() and nothing in it was importable. A security test asserting against a
copy stops testing the system the moment the real one changes, and this copy had
already drifted. It now imports the real function; all 18 assertions still pass,
against the code that actually runs.

Local: build clean, workspace 2550 passed, lint unchanged at 794 errors.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01N4wNHWf7xSwnZCWpJcyv9p

.taskmaster/tasks/task_043.md

@@ -0,0 +1,41 @@
+# Task ID: 43
+
+**Title:** Add regenerate-summary API endpoint
+
+**Status:** done
+
+**Dependencies:** 42 ✓
+
+**Priority:** medium
+
+**Description:** Create POST /api/v1/prompts/:id/regenerate-summary endpoint to force re-generation of summary and chapters for a prompt.
+
+**Details:**
+
+1. Add route in `/src/mcpd/src/routes/prompts.ts`:
+   ```typescript
+   fastify.post('/api/v1/prompts/:id/regenerate-summary', async (request, reply) => {
+     const { id } = request.params as { id: string };
+     const prompt = await promptService.findById(id);
+     if (!prompt) {
+       return reply.status(404).send({ error: 'Prompt not found' });
+     }
+     
+     const { summary, chapters } = await summaryService.generateSummary(prompt.content);
+     const updated = await promptService.updateSummary(id, summary, chapters);
+     
+     return reply.send(updated);
+   });
+   ```
+
+2. Add `updateSummary(id, summary, chapters)` method to PromptRepository and PromptService
+
+3. Return the updated prompt with new summary/chapters in response
+
+**Test Strategy:**
+
+- Unit test: POST to valid prompt ID regenerates summary
+- Unit test: Returns updated prompt with new summary/chapters
+- Unit test: 404 for non-existent prompt ID
+- Unit test: Uses LLM when available, regex fallback otherwise
+- Integration test: End-to-end regeneration updates database