block training-seen checkpoint evaluation

docs/CODEX_EXECUTION_LOG.md

@@ -12704,3 +12704,36 @@ Open:
 - Two adjacent positive AOIs and one real background AOI are not representative
   release evidence. Human review, broader independent geography and exact
   challenger provenance remain blocking.
+
+## 2026-08-09 - Training/evaluation membership gate
+
+### Corrected
+
+- Compared the non-overlap evaluation sample membership against the exact
+  active and challenger training summaries. Turnhout and Westerlo are absent
+  from both train splits; Postel-bos is present in both.
+- Reclassified the Postel detection counts as training-seen regression checks,
+  not independent background validation. No existing metric or checkpoint was
+  promoted on that evidence.
+- Extended the checkpoint evaluator with a strict multi-corpus membership gate.
+  Governed runs now persist a blocked manifest and stop before PyTorch import,
+  model loading and GPU inference if any evaluation AOI is training-seen.
+
+### Reproduced on Tower
+
+- Active training summary SHA-256:
+  `49b2a07d2105d08356431757b83eafc1498eaf1fb76965b1efe05b776824942a`.
+- Challenger training summary SHA-256:
+  `7c917e31216d1df2174c0f9c736f88a81f3835aa991971f8fb8665e17ddf5c9c`.
+- Evaluation summary SHA-256:
+  `c17a8c47eaecc2dfb38778ff5a612f9e6c4d67c9e90e31d3a6a66d8857adec4c`.
+- The strict run blocked on `postel_bos`, with
+  `model_loading_attempted=false` and `gpu_inference_attempted=false`.
+- Blocked-manifest SHA-256:
+  `62e8a9377ac87552936f472b0acf55d1d659ebf27f84ba8c4dbcefe7a374e1da`.
+
+### Remaining limitation
+
+- Independent real-background AOIs are still required. Literal 100% model
+  correctness is not demonstrated; the system now refuses to misrepresent the
+  known overlap as proof.