test(confidence-engine): control report epistemic comparison inputs

Deterministic test (17 cases) proves A/B inputs are correctly controlled:
- supportedEvidence identical in A and B
- findings identical in A and B
- plausibleInterpretations identical (fixed canonical interpretation) in A and B
- scenarioState identical in A and B
- providerConfig identical in A and B
- only unresolvedQuestions visibility differs (A=hidden, B=canonical)
- unresolved questions excluded from evidence and plausible interpretations
- fixed interpretation carries NON-EVIDENCE epistemic status

Also corrects Loop 2 documentation to reflect that three-category
invariance was NOT established (plausibleInterpretations differed
between calls despite identical input), retaining only the narrower
valid finding: no unresolved Open Question was promoted to evidence.

Co-Authored-By: Claude Code <noreply@anthropic.com>

docs/current-handoff.md

@@ -256,7 +256,7 @@ Manual Jenkins deployment pipeline established, version-controlled, and LIVE PRO
 
 - **Branch:** `feature/product-platform-foundation-v0.62`
 - **HEAD:** *(checkpoint commit — see git log for actual SHA)*
-- **Working tree:** clean
+- **Working tree:** clean (after Loop 3 apparatus commit)
 
 ## Architectural Conclusion
 
@@ -295,6 +295,7 @@ tsx runtime                                  — alias-capable experiment execut
 import-only proof                            — prove startCase() import chain resolves without live calls
 OpenAI reconstruction experiment seam        — START_CASE_EXPERIMENT_PROVIDER=openai (experiment-only)
 focused-deconstruction schema fix            — plumbing verified, 48/48 tests pass
+tests/experimental/report-epistemic-ab-input-control.test.js — deterministic A/B input control apparatus (17 tests, zero live calls)
 ```
 
 **No other experimental apparatus is currently valid.** Obsolete setups have been removed or superseded.