chore(phase-4): QA fixes + gitignore portal build artifacts

- Fix 7 test fixtures missing isPublic field added in WS4 Marketplace
- Add portal/.next/ to .gitignore (build artifacts should not be tracked)
- Mark all Phase 4 tasks 11.1-11.11 complete in tasks.md

QA results: 611/611 tests pass, tsc zero errors, portal build OK, CLI build OK

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

tests/unit/controllers/AgentController.test.ts

@@ -34,6 +34,7 @@ const MOCK_AGENT: IAgent = {
   owner: 'team-a',
   deploymentEnv: 'production',
   status: 'active',
+  isPublic: false,
   createdAt: new Date('2026-03-28T09:00:00Z'),
   updatedAt: new Date('2026-03-28T09:00:00Z'),
 };