Document alpha validation and historical fixture dependency

docs/alpha-validation.md

@@ -17,3 +17,24 @@ Before tagging, perform the final local GUI/model smoke with the exact paired
 revisions and configured model/runtime. Reuse copied historical transcripts
 where possible; do not rewrite original regression evidence. Preserve the known
 GTM-Hub human-reference whitespace. Record both candidate SHAs in release notes.
+
+## Historical Lab fixture dependency
+
+Four older experiment tests require six ignored files, absent from a fresh Git
+worktree. Do not add them to the alpha source boundary or silently skip the tests:
+
+- `artifacts/experiments/evidence_observations_v3/20260819_v3_single_run/h_resulting_action/parsed_observations.json`
+- `artifacts/experiments/negative_act_form_v0/20260820_qwen35_9b_single_run/na-01/v3_style_input_observations.json`
+- The same negative-act filename under `na-03`, `na-04`, `na-05`, and `na-06`.
+
+For the alpha audit, these files were copied from the original Lab worktree to a
+separate temporary test directory. That directory exposed the candidate's
+`tests`, `prompts`, `samples`, `src`, and `scripts` as resource links. The full
+suite ran there with the candidate Lab root on `PYTHONPATH` and the candidate's
+absolute tests directory supplied to unittest discovery. All 413 tests passed.
+The bare candidate worktree run instead reports four missing-fixture errors.
+This is a historical test portability limitation, not a runtime dependency.
+
+The paired Assistant suite passed all 107 tests with the candidate Lab backend;
+no Whisper, diarization or Ollama inference was executed. These counts describe
+the preparation validation and do not replace the final smoke-test record.