Refine test cases

[yujuancao07]

Purpose

This PR extends the DeepSeek-V2-Lite E2E coverage with two opt-in four-device cases while keeping the existing three-device PR gate unchanged.

• Add afd-graph-dbo-2a2f for GPU and NPU:
  • Attention: DP=2, TP=1
  • FFN: DP=2, TP=1, EP=2
  • Runs graph + DBO with GSM8K-7
• Add afd-eager-async-cam for NPU:
  • Uses CAMAsyncAFDConnector
  • Attention: DP=1, TP=2
  • FFN: DP=2, TP=1, EP=2
  • Runs in eager mode without graph or DBO
  • Sends one accounting prompt and validates a non-empty 32-token completion
• Extend the shared E2E runner to support the new topologies and completion-based smoke test.
• Update the E2E README, design document, and run-e2e skill.

Test Plan

afd-graph-dbo-2a2f

export AFD_E2E_DEVICES=0,1,2,3
python -m pytest -q -s \
  "tests/e2e/models/deepseek_v2_lite/test_deepseek_v2_lite.py::test_deepseek_v2_lite[afd-graph-dbo-2a2f]"

afd-eager-async-cam

python -m pytest -q -s \
  "tests/e2e/models/deepseek_v2_lite/test_deepseek_v2_lite.py::test_deepseek_v2_lite[afd-graph-dbo]"