feat: add signed ROCm diagnostic lane

.scratch/distributed-gguf-runtime/evidence/DGR-001/known-unrelated-failure.md

@@ -1,7 +1,7 @@
 # Observed pre-existing intermittent tracker race
 
-This file records an earlier unrelated timing observation; it is **not** the
-final DGR-001 verification result.
+This file records an unrelated timing observation and its repeated reproduction;
+it is **not** a DGR-001 benchmark/contract failure.
 
 Test:
 
@@ -15,18 +15,41 @@ One earlier full-suite run produced:
 1 failed, 745 passed, 13 skipped
 ```
 
-A five-run isolated retry matrix reproduced the same rate on both branches:
+A five-run isolated retry matrix reproduced the same rate repeatedly:
 
 ```text
-DGR-001 branch: 4/5 passed, 1/5 failed
-clean d904c40:  4/5 passed, 1/5 failed
+current DGR-001 branch: 4/5 passed, 1/5 failed
+clean d904c40:          4/5 passed, 1/5 failed
 ```
 
-The final full-suite run on the exact hardened DGR-001 state completed green:
+An earlier full-suite run on the signed-provenance DGR-001 state completed
+green:
 
 ```text
-749 passed, 13 skipped in 251.42s
+751 passed, 13 skipped
 ```
 
-The earlier race was therefore timing-sensitive, pre-existing, and unrelated
-to the DGR-001 benchmark/contract files.
+Two full-suite runs after adding the isolated GPU diagnostic profile each hit
+the same race and otherwise passed:
+
+```text
+1 failed, 750 passed, 13 skipped
+```
+
+The latest expanded hardening suite hit the same race and otherwise passed:
+
+```text
+1 failed, 754 passed, 13 skipped
+```
+
+The final hardened state subsequently completed a full green run:
+
+```text
+755 passed, 13 skipped
+```
+
+In each failure, the mock upstream's three-second release timeout completed the
+stream before the cancel POST, so the request was already absent and the cancel
+endpoint returned 404. No tracker/proxy file changed in DGR-001. The race is
+therefore timing-sensitive, pre-existing, and unrelated to the benchmark,
+provenance, or GPU-diagnostic code.