Boundary-safe test generation

[JSONbored]

Phase 4 — Self-host-native differentiators

Context

We already detect missing test evidence (src/signals/test-evidence.ts) but only flag it. Generating tests server-side would break the contributor boundary.

Goal

Offer boundary-safe test generation that closes the test-evidence loop.

Requirements

• When tests are missing, emit a local-write-action spec (the src/mcp/local-write-tools.ts pattern) that the contributor's own agent runs to scaffold tests using the repo's framework/conventions — criteria/content supplied by us; execution on the contributor's machine.
• Config-driven (review.test_generation), default-OFF, public-safe.

Deliverables

• Test-gen action spec + framework/convention hints + tests + docs.

Expected outcome

• Missing-test findings become one action away from resolution; higher test coverage on merged PRs; boundary preserved.

Effort

L.

[linear-code]

JSO-2052