Add experiments/dsv4_p800_max_context_length/ to find the longest input
context that P800 SGLang INT8 can serve for DeepSeek-V4-Flash-INT8.
- Docker-based server start with dynamic --context-length.
- Single-request, single-output-token probes for each candidate length.
- Records success/failure, server args, and metrics per length.
- Generates results.json and report.md summarizing the max supported length.
- Smoke-tested at 4096 tokens successfully.