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_103.md

@@ -0,0 +1,47 @@
+# Task ID: 103
+
+**Title:** Add Shell Completions for ProxyModel Commands
+
+**Status:** cancelled
+
+**Dependencies:** 89 ✗, 90 ✗, 91 ✗, 92 ✗, 93 ✗, 94 ✗, 95 ✗, 96 ✗, 97 ✗, 100 ✓, 101 ✓, 102 ✓
+
+**Priority:** low
+
+**Description:** Extend shell completions to include all new proxymodel-related commands, resources, and flags.
+
+**Details:**
+
+Update `src/cli/src/completions.ts` to add completions for:
+
+```typescript
+// Resource types
+const RESOURCE_TYPES = [...existing, 'proxymodels', 'stages'];
+
+// Command completions
+const COMMANDS = {
+  'get': ['proxymodels', 'stages', ...existing],
+  'describe': ['proxymodel', 'stage', ...existing],
+  'create': ['proxymodel', 'stage', ...existing],
+  'delete': ['proxymodel', 'stage', ...existing],
+  'proxymodel': ['validate'],
+  'cache': ['list', 'clear', 'stats'],
+};
+
+// Dynamic completions for proxymodel/stage names
+async function completeProxymodelName(partial: string): Promise<string[]> {
+  const models = await loadProxyModels();
+  return [...models.keys()].filter(n => n.startsWith(partial));
+}
+
+async function completeStageName(partial: string): Promise<string[]> {
+  const stages = listStages();
+  return stages.map(s => s.name).filter(n => n.startsWith(partial));
+}
+```
+
+Generate completion scripts for bash, zsh, and fish.
+
+**Test Strategy:**
+
+Manual test: completions work in bash/zsh/fish for all new commands. Test proxymodel name completion, stage name completion, subcommand completion.