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_092.md

@@ -0,0 +1,57 @@
+# Task ID: 92
+
+**Title:** Implement mcpctl describe stage Command
+
+**Status:** cancelled
+
+**Dependencies:** 79 ✓
+
+**Priority:** medium
+
+**Description:** Add CLI command to show detailed information about a specific stage including its source location.
+
+**Details:**
+
+Create `src/cli/src/commands/describe-stage.ts`:
+
+```typescript
+import { Command } from 'commander';
+import { listStages, getStage } from 'mcplocal/proxymodel/stage-registry';
+import { join } from 'path';
+
+const STAGES_DIR = join(process.env.HOME ?? '', '.mcpctl', 'stages');
+
+const STAGE_DESCRIPTIONS: Record<string, string> = {
+  'passthrough': 'Returns content unchanged. No processing.',
+  'paginate': 'Splits large content into pages with navigation.',
+  'section-split': 'Splits content on structural boundaries (headers, JSON keys, etc.).',
+  'summarize-tree': 'Recursively summarizes sections with hierarchical navigation.',
+};
+
+export function registerDescribeStage(program: Command): void {
+  program
+    .command('describe stage <name>')
+    .description('Show detailed information about a stage')
+    .action(async (name: string) => {
+      const stages = listStages();
+      const stageInfo = stages.find(s => s.name === name);
+      
+      if (!stageInfo) {
+        console.error(`Stage '${name}' not found`);
+        process.exit(1);
+      }
+      
+      console.log(`Name: ${name}`);
+      console.log(`Source: ${stageInfo.source}`);
+      if (stageInfo.source === 'local') {
+        console.log(`Path: ${join(STAGES_DIR, name + '.ts')}`);
+      }
+      console.log(`Description: ${STAGE_DESCRIPTIONS[name] ?? 'Custom stage'}`);
+      console.log(`Requires LLM: ${requiresLlm(name) ? 'yes' : 'no'}`);
+    });
+}
+```
+
+**Test Strategy:**
+
+CLI test: `mcpctl describe stage passthrough` shows expected output. Test with custom stage, verify path is shown correctly.