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_040.md

@@ -0,0 +1,49 @@
+# Task ID: 40
+
+**Title:** Update Prompt CRUD API to handle priority and linkTarget
+
+**Status:** done
+
+**Dependencies:** 37 ✓
+
+**Priority:** high
+
+**Description:** Modify prompt API endpoints to accept, validate, and return the priority and linkTarget fields. LinkTarget should be immutable after creation.
+
+**Details:**
+
+1. Update `/src/mcpd/src/validation/prompt.schema.ts`:
+   ```typescript
+   export const CreatePromptSchema = z.object({
+     name: z.string().min(1).max(100).regex(/^[a-z0-9-]+$/),
+     content: z.string().min(1).max(50000),
+     projectId: z.string().optional(),
+     priority: z.number().int().min(1).max(10).default(5).optional(),
+     linkTarget: z.string().regex(/^[a-z0-9-]+\/[a-z0-9-]+:[\S]+$/).optional(),
+   });
+   
+   export const UpdatePromptSchema = z.object({
+     content: z.string().min(1).max(50000).optional(),
+     priority: z.number().int().min(1).max(10).optional(),
+     // Note: linkTarget is NOT included - links are immutable
+   });
+   ```
+
+2. Update `/src/mcpd/src/routes/prompts.ts`:
+   - POST /api/v1/prompts: Accept priority, linkTarget
+   - PUT /api/v1/prompts/:id: Accept priority only (not linkTarget)
+   - GET endpoints: Return priority, linkTarget in response
+
+3. Update repository layer to handle new fields
+
+4. Add linkTarget format validation: `project/server:resource-uri`
+
+**Test Strategy:**
+
+- Unit test: POST /api/v1/prompts with priority creates prompt with correct priority
+- Unit test: POST /api/v1/prompts with linkTarget creates linked prompt
+- Unit test: PUT /api/v1/prompts/:id with priority updates priority
+- Unit test: PUT /api/v1/prompts/:id rejects linkTarget (immutable)
+- Unit test: GET /api/v1/prompts returns priority and linkTarget fields
+- Unit test: Invalid linkTarget format rejected (validation error)
+- Unit test: Priority outside 1-10 range rejected