fix: use sglang v0.5.12 release tag instead of dated nightly

Drops the -20260517 nightly suffix so the recipe uses the
lmsysorg/sglang-rocm:v0.5.12-rocm720-mi35x release tag rather than
a date-pinned nightly build.

Author: claude-fix-bot

.github/configs/amd-master.yaml

@@ -471,9 +471,9 @@ glm5.1-fp4-mi355x-sglang:
 # Diverged from glm5.1-fp4-mi355x-sglang (agentic-coding sibling). Reasons below;
 # the original glm5.1-fp4-mi355x-sglang entry is left identical to origin/main so
 # its fixed-seq-len sweep is unaffected.
-#   - image: 'lmsysorg/sglang-rocm:v0.5.10rc0-rocm720-mi35x-20260415' -> 'lmsysorg/sglang-rocm:v0.5.12-rocm720-mi35x-20260517'
+#   - image: 'lmsysorg/sglang-rocm:v0.5.10rc0-rocm720-mi35x-20260415' -> 'lmsysorg/sglang-rocm:v0.5.12-rocm720-mi35x'
 glm5.1-fp4-mi355x-sglang-agentic:
-  image: lmsysorg/sglang-rocm:v0.5.12-rocm720-mi35x-20260517
+  image: lmsysorg/sglang-rocm:v0.5.12-rocm720-mi35x
   model: amd/GLM-5.1-MXFP4
   model-prefix: glm5.1
   runner: mi355x