Task 8 — Tests and E2E validation

[hiydavid]

Part of #179.

Goal

Add test coverage for the new behavior: finding → lever mapping, preflight hard-blocks, Delta snapshot write/read, and the full CTA → Optimizer E2E flow.

Work

• Leave backend/tests/test_fix_agent_prompt.py and backend/tests/test_fix_agent_paths.py in place (backend stays per Task 1), but add a one-liner "Fix Agent UI deprecated — see Workbench 0.2 for full removal" comment at the top of each file
• New unit test for the finding → lever mapping logic (wherever it lives — likely backend/routers/auto_optimize.py or a new backend/services/optimizer_signals.py)
• New unit test for preflight hard-block — mock scanner to return a scan result with Check 1 fail → expect 400; Check 10 fail → expect 400; all pass → expect job submission
• Integration test for Delta snapshot write/read path against a real workspace (extend tests/test_e2e_deployed.py or add a new tests/test_optimizer_scan_snapshots.py)
• Playwright E2E: IQ Score tab CTA click → lands on Optimize tab with correct levers pre-selected. Extend tests/test_e2e_deployed.py.
• Playwright E2E: trigger an Optimizer run, confirm RunDetailView shows preflight scan snapshot

Acceptance

• pytest backend/tests/ passes
• Deployed E2E tests pass against a workspace with a known space
• Preflight block scenarios are covered
• Delta persistence is exercised end-to-end

Files

• backend/tests/test_fix_agent_prompt.py (add deprecation comment)
• backend/tests/test_fix_agent_paths.py (add deprecation comment)
• backend/tests/test_optimizer_signals.py (new)
• backend/tests/test_optimizer_preflight.py (new)
• tests/test_e2e_deployed.py (extend)
• tests/test_optimizer_scan_snapshots.py (new, optional split)