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_078.md

@@ -0,0 +1,78 @@
+# Task ID: 78
+
+**Title:** Create ProxyModel YAML Schema and Loader
+
+**Status:** done
+
+**Dependencies:** 71 ✓
+
+**Priority:** high
+
+**Description:** Define the YAML schema for proxymodel definitions and implement the loader that reads from ~/.mcpctl/proxymodels/ and merges with built-ins.
+
+**Details:**
+
+Create `src/mcplocal/src/proxymodel/schema.ts`:
+
+```typescript
+import { z } from 'zod';
+
+export const ProxyModelSchema = z.object({
+  kind: z.literal('ProxyModel'),
+  metadata: z.object({
+    name: z.string(),
+  }),
+  spec: z.object({
+    controller: z.string().optional().default('gate'),
+    controllerConfig: z.record(z.unknown()).optional(),
+    stages: z.array(z.object({
+      type: z.string(),
+      config: z.record(z.unknown()).optional(),
+    })),
+    appliesTo: z.array(z.enum(['prompts', 'toolResults', 'resource'])).optional(),
+    cacheable: z.boolean().optional().default(true),
+  }),
+});
+
+export type ProxyModelDefinition = z.infer<typeof ProxyModelSchema>;
+```
+
+Create `src/mcplocal/src/proxymodel/loader.ts`:
+
+```typescript
+import { readdir, readFile } from 'fs/promises';
+import { join } from 'path';
+import { parse as parseYaml } from 'yaml';
+import { ProxyModelSchema, type ProxyModelDefinition } from './schema';
+import { getBuiltInProxyModels } from './built-in-models';
+
+const PROXYMODELS_DIR = join(process.env.HOME ?? '', '.mcpctl', 'proxymodels');
+
+export async function loadProxyModels(): Promise<Map<string, ProxyModelDefinition>> {
+  const models = new Map<string, ProxyModelDefinition>();
+  
+  // Load built-ins first
+  for (const [name, model] of getBuiltInProxyModels()) {
+    models.set(name, model);
+  }
+  
+  // Load local (overrides built-ins)
+  try {
+    const files = await readdir(PROXYMODELS_DIR);
+    for (const file of files.filter(f => f.endsWith('.yaml') || f.endsWith('.yml'))) {
+      const content = await readFile(join(PROXYMODELS_DIR, file), 'utf-8');
+      const parsed = parseYaml(content);
+      const validated = ProxyModelSchema.parse(parsed);
+      models.set(validated.metadata.name, validated);
+    }
+  } catch (e) {
+    // Directory doesn't exist or can't be read - use built-ins only
+  }
+  
+  return models;
+}
+```
+
+**Test Strategy:**
+
+Unit tests: valid YAML parses correctly, invalid YAML throws validation error, local models override built-ins with same name, missing directory doesn't throw. Create test fixtures for various YAML configurations.