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_081.md

@@ -0,0 +1,59 @@
+# Task ID: 81
+
+**Title:** Define Built-in ProxyModels (default, subindex)
+
+**Status:** done
+
+**Dependencies:** 78 ✓
+
+**Priority:** high
+
+**Description:** Create the built-in proxymodel definitions for 'default' (current behavior) and 'subindex' (hierarchical navigation).
+
+**Details:**
+
+Create `src/mcplocal/src/proxymodel/built-in-models.ts`:
+
+```typescript
+import type { ProxyModelDefinition } from './schema';
+
+export function getBuiltInProxyModels(): Map<string, ProxyModelDefinition> {
+  const models = new Map<string, ProxyModelDefinition>();
+  
+  models.set('default', {
+    kind: 'ProxyModel',
+    metadata: { name: 'default' },
+    spec: {
+      controller: 'gate',
+      controllerConfig: { byteBudget: 8192 },
+      stages: [
+        { type: 'passthrough' },
+        { type: 'paginate', config: { pageSize: 8000 } },
+      ],
+      appliesTo: ['prompts', 'toolResults'],
+      cacheable: false,
+    },
+  });
+  
+  models.set('subindex', {
+    kind: 'ProxyModel',
+    metadata: { name: 'subindex' },
+    spec: {
+      controller: 'gate',
+      controllerConfig: { byteBudget: 8192 },
+      stages: [
+        { type: 'section-split', config: { minSectionSize: 2000, maxSectionSize: 15000 } },
+        { type: 'summarize-tree', config: { maxSummaryTokens: 200, maxGroupSize: 5, maxDepth: 3 } },
+      ],
+      appliesTo: ['prompts', 'toolResults'],
+      cacheable: true,
+    },
+  });
+  
+  return models;
+}
+```
+
+**Test Strategy:**
+
+Unit tests: both models are returned by getBuiltInProxyModels(), 'default' has passthrough+paginate stages, 'subindex' has section-split+summarize-tree stages, both schemas validate correctly.