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_073.md

@@ -0,0 +1,67 @@
+# Task ID: 73
+
+**Title:** Implement In-Memory CacheProvider
+
+**Status:** done
+
+**Dependencies:** 71 ✓
+
+**Priority:** high
+
+**Description:** Create the CacheProvider implementation that stages use for caching expensive computations. Start with in-memory cache for Phase 1, with content-addressed keys.
+
+**Details:**
+
+Create `src/mcplocal/src/proxymodel/cache-provider.ts`:
+
+```typescript
+import { createHash } from 'crypto';
+import type { CacheProvider } from './types';
+
+export class InMemoryCacheProvider implements CacheProvider {
+  private cache = new Map<string, { value: string; timestamp: number }>();
+  private maxSize: number;
+  private ttlMs: number;
+
+  constructor(options: { maxSize?: number; ttlMs?: number } = {}) {
+    this.maxSize = options.maxSize ?? 1000;
+    this.ttlMs = options.ttlMs ?? 3600000; // 1 hour default
+  }
+
+  hash(content: string): string {
+    return createHash('sha256').update(content).digest('hex').slice(0, 16);
+  }
+
+  async get(key: string): Promise<string | null> {
+    const entry = this.cache.get(key);
+    if (!entry) return null;
+    if (Date.now() - entry.timestamp > this.ttlMs) {
+      this.cache.delete(key);
+      return null;
+    }
+    return entry.value;
+  }
+
+  async set(key: string, value: string): Promise<void> {
+    if (this.cache.size >= this.maxSize) this.evictOldest();
+    this.cache.set(key, { value, timestamp: Date.now() });
+  }
+
+  async getOrCompute(key: string, compute: () => Promise<string>): Promise<string> {
+    const cached = await this.get(key);
+    if (cached !== null) return cached;
+    const value = await compute();
+    await this.set(key, value);
+    return value;
+  }
+
+  private evictOldest(): void {
+    const oldest = [...this.cache.entries()].sort((a, b) => a[1].timestamp - b[1].timestamp)[0];
+    if (oldest) this.cache.delete(oldest[0]);
+  }
+}
+```
+
+**Test Strategy:**
+
+Unit tests for: hash() produces consistent output, get() returns null for missing keys, set()/get() round-trip works, TTL expiration works, LRU eviction triggers at maxSize, getOrCompute() caches and returns cached values.