docs: reorganize module design documents

Signed-off-by: hsliuustc0106 <liuhongsheng4@huawei.com>

docs/design/module/benchmarking.md

@@ -0,0 +1,47 @@
+---
+title: Benchmarking
+kind: module
+status: draft
+owners:
+  - "@alex-jw-brooks"
+primary_code_paths:
+  - vllm_omni/benchmarks/**
+  - vllm_omni/entrypoints/cli/benchmark/**
+related_code_paths:
+  - benchmarks/**
+depends_on:
+  - entrypoints.md
+  - profiling.md
+validation_paths:
+  - tests/benchmarks/**
+  - tests/dfx/perf/**
+upstream_refs:
+  - vllm.benchmarks
+last_reviewed: 2026-07-16
+---
+
+# Benchmarking
+
+Benchmarking defines reproducible workloads, metrics, warm-up, measurement,
+and result metadata for comparing vLLM-Omni performance.
+
+## Candidate invariants
+
+### BENCH-INV-001: Results are reproducible
+
+**Rule:** Results MUST identify the model, revision, commit, hardware,
+configuration, workload, concurrency, warm-up, and measurement window.
+
+### BENCH-INV-002: Correctness precedes performance
+
+**Rule:** A benchmark MUST validate successful and semantically acceptable
+outputs before using timings as performance evidence.
+
+### BENCH-INV-003: Metric definitions are explicit
+
+**Rule:** Metrics MUST state their unit, population, and aggregation.
+
+## Safe-change guide
+
+Test workload parsing and metric calculations with deterministic fixtures. Do
+not compare materially different workloads or runtime settings.