experiment: classify answer evidence direction

Move EVIDENCE_DIRECTION_GROUPS out of the mock fixture library into
lib/graph/evidence-direction.js where it belongs. Remove unused
DECISION_CONDITIONS and CONTRADICTION_KEYWORDS exports from scenarios.

Add Experiment 24A entry to the design log.

docs/design-evolution-log.md

@@ -1275,6 +1275,52 @@ The assessment works correctly across all test cases: 39/39 passing. It provides
 
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+## Experiment 24A — Evidence Direction Classification
+
+**Status:** Completed (passive layer)
+
+### Hypothesis
+
+Answer evidence can be distinguished from resolved-question wording and classified by whether it supports, contradicts or merely informs a decision condition.
+
+### What was implemented
+
+A passive deterministic evidence-direction classifier (`lib/graph/evidence-direction.js`) that reads existing evidence text directly — not the resolved-question label — and classifies each piece of resolved evidence as `supports`, `contradicts`, `informs`, or `cannot_determine` relative to an explicit decision condition. Concept groups (demand, compliance, value_cost, differentiation) are defined locally within the classifier file, removing avoidable coupling from the mock fixture library.
+
+### Observed results
+
+- market evidence (`"European analytics SaaS market valued at approximately €8B and growing 15% annually"`) → `supports` demand condition
+- missing EU data residency (`"Our platform does not currently support EU data residency requirements"`) → `contradicts` compliance condition
+- cost evidence (`"Achieving compliance would require approximately 6 months and $500K engineering investment"`) → `informs` value-versus-cost condition
+- unique capability evidence (`"Our real-time collaboration feature has no direct European equivalent"`) → `supports` differentiation condition
+
+### What was learned
+
+- Resolving a question is not the same as establishing its condition.
+- Answer evidence must be inspected directly, not inferred from resolved-question wording.
+- Relevant evidence may inform without proving.
+- Contradiction must remain attached to the condition it concerns.
+
+### Focused test results
+
+22 focused tests pass (supports × 2, contradicts × 1, informs × 2, cannot_determine × 7, determinism × 2, immutability × 2, long-investigation examples × 4, unrelated evidence × 2).
+
+### Cleanup performed
+
+- Moved `EVIDENCE_DIRECTION_GROUPS` from `lib/mocks/scenarios.js` into `lib/graph/evidence-direction.js`.
+- Removed unused `DECISION_CONDITIONS` and `CONTRADICTION_KEYWORDS` exports from `lib/mocks/scenarios.js`.
+- Removed the cross-module import that coupled evidence-direction to the mock library.
+
+### Experiment 23 compatibility
+
+`decision-condition-status.test.js` (39 tests) and `question-decision-conditions.test.js` (40 tests) both continue to pass. No behaviour change in Experiment 23 or 22 classifiers.
+
+### Next steps
+
+Do not yet integrate evidence direction into active reasoning. That belongs to a separate follow-on experiment. Do not amend Experiment 23 condition statuses here.
+
+---
+
 ## Current Open Questions
 
 The following are active explorations rather than decisions.