Add FIXTURE_MODE=updateOnly support that bypasses Start and sends the
committed fixture (tests/fixtures/pre-anchored-update-savings-realism.json)
directly as an Update request body through production HTTP route.
scripts/reproduce-multi-turn-investigation.mjs:
- Added ESM imports for deterministic fixture loading (fs, fileURLToPath, path)
- Added FIXTURE_PATH constant pointing to committed fixture
- Added fixtureMode env-var selector and runUpdateOnlyMode() function
- Validates ANSWER_2 before any live call (zero calls if missing)
- Verifies single savings-realism anchor invariant on load
- Preserves all hardened capture fields in pre-anchored mode
- Normal-mode Start→Update chain preserved under guard clause
tests/reproduce-multi-turn-investigation.harness.test.js:
- Added 7 new harness tests for pre-anchored scenarios (46 total, all pass)
- Updated runPreAnchoredSimulation to persist rejectedProposalSnapshot on rejection
- Added runPreAnchoredSimulationWithBlock() helper
docs/:
- New docs/experiment-57j78.md with full apparatus description
- Updated docs/current-handoff.md with 57J.78 section
