The AI emits [FIX_OUTCOME] when the engineer indicates in chat that a
prior suggested fix worked, didn't work, or was partially applied. The
marker writes to session_suggested_fixes.ai_outcome_proposal (JSONB),
which the frontend surfaces as a "confirm outcome?" banner. The status
column is only updated when the engineer clicks confirm (via PATCH
/outcome endpoint from Task 3).
Placeholder-only system prompt wiring comes in Task 5.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>