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_146.md

@@ -0,0 +1,29 @@
+# Task ID: 146
+
+**Title:** AgentRuntime interface definition
+
+**Status:** pending
+
+**Dependencies:** None
+
+**Priority:** medium
+
+**Description:** Define AgentRuntime adapter interface for swappable agent implementations
+
+**Details:**
+
+Create src/mcpd/src/services/agent-runtime.ts:
+1. Define RuntimeSessionOpts: { agentId, projectId, taskId?, image, persona (prompt files) }
+2. Define RuntimeStatus: 'starting' | 'running' | 'completed' | 'failed'
+3. Define RuntimeResult: { branch: string, headCommit: string, summary: string, prUrl?: string }
+4. Define AgentRuntime interface:
+   - startSession(opts: RuntimeSessionOpts): Promise<{ sessionId: string }>
+   - send(sessionId: string, message: string): Promise<void>
+   - status(sessionId: string): Promise<RuntimeStatus>
+   - result(sessionId: string): Promise<RuntimeResult>
+   - endSession(sessionId: string): Promise<void>
+5. This is an interface, not an implementation - allows swapping runtimes later
+
+**Test Strategy:**
+
+Type tests: verify interface can be implemented, verify all methods have correct signatures.