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_039.md

@@ -0,0 +1,38 @@
+# Task ID: 39
+
+**Title:** Add gated field to Project schema
+
+**Status:** done
+
+**Dependencies:** None
+
+**Priority:** high
+
+**Description:** Extend the Prisma schema for the Project model to include the gated boolean field (default true) that controls whether sessions go through the keyword-driven prompt retrieval flow.
+
+**Details:**
+
+1. Update `/src/db/prisma/schema.prisma` to add to Project:
+   - `gated Boolean @default(true)`
+
+2. Create Prisma migration:
+   ```bash
+   pnpm --filter db exec prisma migrate dev --name add-project-gated
+   ```
+
+3. Update project-related TypeScript types
+
+4. Update project validation schemas to include gated field:
+   ```typescript
+   gated: z.boolean().default(true).optional(),
+   ```
+
+5. Update project API routes to accept and return the gated field
+
+**Test Strategy:**
+
+- Unit test: Migration creates gated column with default true
+- Unit test: Project creation with gated=false
+- Unit test: Project creation uses default gated=true when not specified
+- Unit test: Project update can toggle gated field
+- Integration test: GET /api/v1/projects/:name returns gated field