fix: enable interactive TaskV2 and harden Bash execution

[ericleepi314]

Summary

• expose TaskV2 in interactive agent-server sessions while retaining TodoWrite for --print
• project TaskV2 create/update/list/delete events into the TUI checklist
• preserve compound Bash cd semantics and allow short bounded sleeps
• add backend and frontend regression coverage

Validation

• pytest -q tests/test_task_v2_session_gating.py tests/test_tool_system_tools.py tests/test_bash_sleep_detection.py (83 passed)
• npm test -- --run src/__tests__/todoSurface.test.ts src/__tests__/gatewayClient.test.ts (68 passed)
• npm run typecheck
• npm run build
• targeted ESLint: no errors
• git diff --check