[P6.8.1] Add tests for untested core modules: artifacts.py, review.py, api_key_service.py

[frankbria]

Problem

Three sizeable core modules have no direct test coverage, two of them on the Ship path and one security-adjacent:

Module	LOC	Used by	Risk
core/api_key_service.py	211	cli/auth_commands.py, auth/api_key_router.py	High — security-adjacent (note: the platform_store API-key path is well covered; this core service is the untested duplicate)
core/artifacts.py	428	cli/app.py (cf patch export)	Medium — largest untested module, on the Ship path
core/review.py	285	ui/routers/review_v2.py	Medium — cf review surface

core/prd_stress_test.py (499 LOC) is also under-covered relative to size (single thin referencing test).

Fix

• Add direct unit tests for api_key_service.py, artifacts.py, review.py (MockProvider, no live API calls); expand prd_stress_test.py coverage.

Acceptance criteria

• api_key_service.py, artifacts.py, review.py have direct tests covering main paths + error cases.
• New tests carry the @pytest.mark.v2 marker.

Source: release-readiness audit 2026-06-13 (test/CI agent).

[coderabbitai]

🔗 Related PRs

#304 - test(cli): add comprehensive v2 CLI integration test suite [merged]
#317 - feat(cli): add interactive PRD generation via Socratic discovery [merged]
#320 - test(core): add integration tests for credentials and environment modules [merged]
#386 - [Phase 2.5-F] Harden verification gates and add batch-level QA [merged]
#427 - test(core): add 26 edge case tests across core components [merged]

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