Fix baseline-phase unit-test suite-ordering dependency

[SoundMindsAI]

Summary

The baseline-phase orchestrator unit tests pass as part of the full suite but can fail when run in isolation (or in a different order) — a classic hermeticity bug, usually a module-level Settings() / env read that leaks state between tests.

Reproduce

.venv/bin/pytest backend/tests/unit/workers/test_orchestrator_baseline_phase.py -v

Fix

Confirmed two-layer root cause (see the spec, not just "module-level state"):

1. _compute_baseline_wait_s in backend/workers/orchestrator.py calls get_settings() even when the study already carries an explicit trial_timeout_s — forcing a Settings() construction those tests don't need.
2. backend/tests/unit/test_main_lifespan.py leaks DATABASE_URL_FILE / POSTGRES_PASSWORD_FILE into os.environ at collection time, so in isolation that construction raises ValidationError.

In the full suite test_main_lifespan is collected first, so the env is already set and the tests pass — hence the ordering dependency.

Durable fix: make the settings read in _compute_baseline_wait_s lazy (only when no explicit trial_timeout_s), so the baseline tests never construct Settings(). The leaking fixture in test_main_lifespan.py is documented but left out of scope (fixing it could unmask other silent free-riders).

Definition of done

• The baseline-phase test file passes in isolation AND as part of make test-unit
• No shared mutable/import-time state between tests
• make test-unit green

Background

Captured at docs/00_overview/planned_features/02_mvp2/bug_baseline_phase_test_isolation/idea.md.

Good first issue: teaches hermetic-test patterns + pytest fixtures; bounded reproduction.

[SoundMindsAI]

Advanced Idea → Plan — a cross-model-reviewed feature spec + implementation plan landed via #413 (merged 69af77eb, 2026-06-02). 2 stories / 1 epic + a regression test that fails pre-fix. Confirmed two-layer root cause: _compute_baseline_wait_s reads get_settings() even with an explicit trial_timeout_s, AND test_main_lifespan.py leaks env vars into os.environ at collection time. GPT-5.5: spec 2 cycles 2/2 accepted, plan 2 cycles (1 rejected w/ counter-evidence).

Artifacts:

• Spec: docs/00_overview/planned_features/02_mvp2/bug_baseline_phase_test_isolation/feature_spec.md
• Plan: docs/00_overview/planned_features/02_mvp2/bug_baseline_phase_test_isolation/implementation_plan.md

This is now ready to implement:

/impl-execute docs/00_overview/planned_features/02_mvp2/bug_baseline_phase_test_isolation/implementation_plan.md --all

No source code or migration was written — planning artifacts only.

[SoundMindsAI]

Shipped — finalized at docs/00_overview/implemented_features/2026_06_05_bug_baseline_phase_test_isolation/. Closing as completed (tracking-issue close-on-merge was missed at merge time; backfilled during a planned_features↔issues reconciliation).