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_116.md

@@ -0,0 +1,26 @@
+# Task ID: 116
+
+**Title:** One-shot RBAC binding backfill migration
+
+**Status:** pending
+
+**Dependencies:** 115
+
+**Priority:** high
+
+**Description:** Implement guarded startup migration to rewrite existing 'tasks' bindings to 'inference-tasks' so pre-existing grants continue authorizing inference endpoints
+
+**Details:**
+
+In src/mcpd/src/main.ts or a new bootstrap module:
+1. Read system settings from SYSTEM_SETTINGS_SECRET (see src/mcpd/src/bootstrap/system-settings.ts pattern)
+2. Check for boolean key 'rbacTasksBackfillComplete'
+3. If false/missing: iterate rbacRepo.findAll(), for each RbacDefinition row, rewrite roleBindings where resource === 'tasks' to resource: 'inference-tasks'
+4. Use rbacRepo.update() to persist changes
+5. Set 'rbacTasksBackfillComplete': true in system settings after completion
+6. Wildcard bindings (resource: '*') are untouched
+7. Model on migrateAdminRole pattern in main.ts
+
+**Test Strategy:**
+
+Unit test: create RbacDefinition with resource:'tasks', run backfill, verify resource changed to 'inference-tasks'. Test idempotency: run twice, verify no duplicate rewrites. Test wildcard unchanged.