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_099.md

@@ -0,0 +1,61 @@
+# Task ID: 99
+
+**Title:** Add Cache Key with Stage File Hash
+
+**Status:** done
+
+**Dependencies:** 98 ✓
+
+**Priority:** medium
+
+**Description:** Include the stage file hash in cache keys so cached artifacts are automatically invalidated when stage code changes.
+
+**Details:**
+
+Modify `src/mcplocal/src/proxymodel/executor.ts`:
+
+```typescript
+import { readFile, stat } from 'fs/promises';
+import { createHash } from 'crypto';
+import { join } from 'path';
+
+const STAGES_DIR = join(process.env.HOME ?? '', '.mcpctl', 'stages');
+const stageFileHashes: Map<string, string> = new Map();
+
+async function getStageFileHash(stageName: string): Promise<string> {
+  // Check if custom stage file exists
+  const filePath = join(STAGES_DIR, `${stageName}.ts`);
+  try {
+    const content = await readFile(filePath, 'utf-8');
+    const hash = createHash('sha256').update(content).digest('hex').slice(0, 8);
+    stageFileHashes.set(stageName, hash);
+    return hash;
+  } catch {
+    // Built-in stage, use version-based hash or fixed value
+    return 'builtin-v1';
+  }
+}
+
+// In executePipeline, compute cache key:
+const stageHash = await getStageFileHash(stageConfig.type);
+const cacheKey = [
+  'stage',
+  stageConfig.type,
+  stageHash,
+  cache.hash(currentContent),
+  cache.hash(JSON.stringify(stageConfig.config ?? {})),
+].join(':');
+
+// Use pipeline-level cache wrapping:
+if (proxyModel.spec.cacheable) {
+  const cached = await cache.get(cacheKey);
+  if (cached) {
+    currentContent = cached;
+    continue; // Skip stage execution
+  }
+}
+```
+
+**Test Strategy:**
+
+Unit tests: changing stage file content changes the hash, built-in stages have stable hash, cache miss when stage file changes, cache hit when stage file unchanged.