Add perf-changelog entry for DSv4 FP4 MI355X SGLang AgentX MTP image update

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

Author: github-actions[bot]

inferencex-e2e/perf-changelog.yaml

@@ -9538,3 +9538,9 @@
     - "Run prefill context parallelism on the TP-only arms at conc 16, 32 and 48; conc 1 and 4 keep BCG."
     - "Enable SGLANG_OPT_FP8_WO_A_FUSED_INVROPE."
   pr-link: https://github.com/SemiAnalysisAI/InferenceX/pull/3778
+
+- config-keys:
+    - dsv4-fp4-mi355x-sglang-agentic-mtp
+  description:
+    - "Update the SGLang ROCm image from v0.5.21-rocm720-mi35x-20261007 to v0.5.21-rocm720-mi35x-20261010."
+  pr-link: https://github.com/SemiAnalysisAI/InferenceX/pull/3916