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_071.md

@@ -0,0 +1,70 @@
+# Task ID: 71
+
+**Title:** Define ProxyModel Public Type Contract
+
+**Status:** done
+
+**Dependencies:** None
+
+**Priority:** high
+
+**Description:** Create the core TypeScript types for the ProxyModel framework that stages will import from `mcpctl/proxymodel`. This establishes the public API contract that stage authors write against.
+
+**Details:**
+
+Create `src/mcplocal/src/proxymodel/types.ts` with:
+
+```typescript
+export interface StageHandler {
+  (content: string, ctx: StageContext): Promise<StageResult>;
+}
+
+export interface StageContext {
+  contentType: 'prompt' | 'toolResult' | 'resource';
+  sourceName: string;
+  projectName: string;
+  sessionId: string;
+  originalContent: string;
+  llm: LLMProvider;
+  cache: CacheProvider;
+  log: Logger;
+  config: Record<string, unknown>;
+}
+
+export interface StageResult {
+  content: string;
+  sections?: Section[];
+  metadata?: Record<string, unknown>;
+}
+
+export interface Section {
+  id: string;
+  title: string;
+  content: string;
+}
+
+export interface LLMProvider {
+  complete(prompt: string, options?: { system?: string; maxTokens?: number }): Promise<string>;
+  available(): boolean;
+}
+
+export interface CacheProvider {
+  getOrCompute(key: string, compute: () => Promise<string>): Promise<string>;
+  hash(content: string): string;
+  get(key: string): Promise<string | null>;
+  set(key: string, value: string): Promise<void>;
+}
+
+export interface Logger {
+  debug(msg: string): void;
+  info(msg: string): void;
+  warn(msg: string): void;
+  error(msg: string): void;
+}
+```
+
+Also create `src/mcplocal/src/proxymodel/index.ts` as the public entrypoint that re-exports these types. Update `package.json` exports to expose `mcpctl/proxymodel`.
+
+**Test Strategy:**
+
+Unit tests verifying type exports are accessible from the public entrypoint. Create a sample stage file that imports from `mcpctl/proxymodel` and verify it compiles without errors.