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_095.md

@@ -0,0 +1,70 @@
+# Task ID: 95
+
+**Title:** Implement mcpctl proxymodel validate Command
+
+**Status:** cancelled
+
+**Dependencies:** 78 ✓, 79 ✓
+
+**Priority:** medium
+
+**Description:** Add CLI command to validate a proxymodel definition, checking that all stages resolve and config is valid.
+
+**Details:**
+
+Create `src/cli/src/commands/proxymodel-validate.ts`:
+
+```typescript
+import { Command } from 'commander';
+import { loadProxyModels } from 'mcplocal/proxymodel/loader';
+import { getStage, loadCustomStages } from 'mcplocal/proxymodel/stage-registry';
+
+export function registerProxymodelValidate(program: Command): void {
+  program
+    .command('proxymodel validate <name>')
+    .description('Validate a proxymodel definition')
+    .action(async (name: string) => {
+      await loadCustomStages();
+      const models = await loadProxyModels();
+      const model = models.get(name);
+      
+      if (!model) {
+        console.error(`Proxymodel '${name}' not found`);
+        process.exit(1);
+      }
+      
+      let valid = true;
+      const errors: string[] = [];
+      
+      // Check all stages resolve
+      for (const stageConfig of model.spec.stages) {
+        const stage = getStage(stageConfig.type);
+        if (!stage) {
+          errors.push(`Stage '${stageConfig.type}' not found`);
+          valid = false;
+        }
+      }
+      
+      // Check controller is valid
+      const validControllers = ['gate', 'none'];
+      if (model.spec.controller && !validControllers.includes(model.spec.controller)) {
+        errors.push(`Unknown controller '${model.spec.controller}'`);
+        valid = false;
+      }
+      
+      if (valid) {
+        console.log(`✓ Proxymodel '${name}' is valid`);
+      } else {
+        console.error(`✗ Proxymodel '${name}' has errors:`);
+        for (const err of errors) {
+          console.error(`  - ${err}`);
+        }
+        process.exit(1);
+      }
+    });
+}
+```
+
+**Test Strategy:**
+
+CLI test: valid proxymodel passes, proxymodel with unknown stage fails with clear error, proxymodel with unknown controller fails. Test with both built-in and custom stages.