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_110.md

@@ -0,0 +1,62 @@
+# Task ID: 110
+
+**Title:** Implement RBAC for ProxyModels
+
+**Status:** deferred
+
+**Dependencies:** 87 ✗
+
+**Priority:** low
+
+**Description:** Add 'run' permission on proxymodels resource controlling which proxymodels users can activate on projects.
+
+**Details:**
+
+Update RBAC schema and enforcement:
+
+1. Add to `src/db/prisma/schema.prisma`:
+```prisma
+// Extend existing RbacBinding or Permission model
+enum RbacResource {
+  // ... existing
+  proxymodels
+}
+
+enum RbacPermission {
+  // ... existing
+  run     // permission to use a proxymodel
+  cache   // permission to push to shared cache
+}
+```
+
+2. Add enforcement in `src/mcplocal/src/router.ts`:
+```typescript
+async function resolveProxyModel(
+  requestedModel: string,
+  projectName: string,
+  userId: string
+): Promise<ProxyModelDefinition> {
+  const models = await loadProxyModels();
+  const model = models.get(requestedModel);
+  
+  if (!model) {
+    console.warn(`Proxymodel '${requestedModel}' not found, using default`);
+    return models.get('default')!;
+  }
+  
+  // Check RBAC permission
+  const hasPermission = await checkPermission(userId, 'run', 'proxymodels', requestedModel);
+  if (!hasPermission) {
+    console.warn(`User lacks 'run' permission for proxymodel '${requestedModel}', using default`);
+    return models.get('default')!;
+  }
+  
+  return model;
+}
+```
+
+3. 'default' proxymodel requires no permission (always allowed).
+
+**Test Strategy:**
+
+Integration test: user with 'run' permission can use proxymodel, user without permission falls back to default, 'default' always works, permission check logs reason for fallback.