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_125.md

@@ -0,0 +1,25 @@
+# Task ID: 125
+
+**Title:** Epic zod validation schemas
+
+**Status:** pending
+
+**Dependencies:** 117
+
+**Priority:** medium
+
+**Description:** Create Epic validation schemas in src/mcpd/src/validation/ for request/response validation
+
+**Details:**
+
+Create src/mcpd/src/validation/epic.schema.ts:
+1. DoneCriterionSchema: z.object({ id: z.string(), text: z.string(), kind: z.enum(['outcome', 'quality']), met: z.boolean() })
+2. AcceptedTradeoffSchema: z.object({ what: z.string(), why: z.string(), who: z.string(), deScopedBy: z.string().optional(), at: z.string() })
+3. CreateEpicSchema: name, content, doneCriteria (array), projectId or project (name), description optional
+4. UpdateEpicSchema: partial of create fields plus status
+5. EpicResponseSchema for API responses
+6. Follow prompt.schema.ts patterns
+
+**Test Strategy:**
+
+Unit tests: validate CreateEpicSchema accepts valid input, rejects missing required fields, validates doneCriteria array structure, validates status enum values.