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_044.md

@@ -0,0 +1,48 @@
+# Task ID: 44
+
+**Title:** Create prompt-index API endpoint
+
+**Status:** done
+
+**Dependencies:** 42 ✓
+
+**Priority:** medium
+
+**Description:** Create GET /api/v1/projects/:name/prompt-index endpoint that returns a compact index of prompts (name, priority, summary, chapters) for a project.
+
+**Details:**
+
+1. Add route in `/src/mcpd/src/routes/prompts.ts`:
+   ```typescript
+   fastify.get('/api/v1/projects/:name/prompt-index', async (request, reply) => {
+     const { name } = request.params as { name: string };
+     const project = await projectService.findByName(name);
+     if (!project) {
+       return reply.status(404).send({ error: 'Project not found' });
+     }
+     
+     const prompts = await promptService.findByProject(project.id);
+     const index = prompts.map(p => ({
+       name: p.name,
+       priority: p.priority,
+       summary: p.summary,
+       chapters: p.chapters,
+       linkTarget: p.linkTarget,
+     }));
+     
+     return reply.send({ prompts: index });
+   });
+   ```
+
+2. Consider adding global prompts to the index (inherited by all projects)
+
+3. Sort by priority descending in response
+
+**Test Strategy:**
+
+- Unit test: Returns compact index for valid project
+- Unit test: Index contains name, priority, summary, chapters, linkTarget
+- Unit test: 404 for non-existent project
+- Unit test: Empty array for project with no prompts
+- Unit test: Results sorted by priority descending
+- Integration test: End-to-end retrieval matches database state