fix(sglang): tighten rollout argument guidance

[CjhHa1]

Summary

• inline the two single-use dropped-argument helpers into the backend filter that owns the behavior
• align the safe server-port bound with pinned SGLang 0.5.12.post1's actual grpc_port = port + 10000 derivation
• narrow the Qwen3 guidance to a 4B dense baseline and document larger/MoE warmup, attention-backend, CUDA-graph, and temporary-port exceptions without changing recipe values

Related Issue

N/A — follow-up to #392.

Test Plan

• SKIP=no-commit-to-branch uvx pre-commit run --all-files --show-diff-on-failure — passed
• CPU assertion harness for UniRL-only key filtering, unknown-key warn/strict behavior, required-key precedence, the 55535 port boundary, repeated port reservation, and YAML parsing of all 9 touched recipes — passed
• GPU rollout: Not run; production behavior is unchanged apart from expanding the valid server-port range to match the pinned SGLang derivation. Recipe edits are comments only.

The focused assertions remain one-off because the repository intentionally keeps no committed top-level test tree.

Compatibility / Risk

Default warn/strict behavior and filtered output are unchanged. The server-port candidate range expands from 1024–35535 to 1024–55535; under pinned SGLang 0.5.12.post1, an automatically derived gRPC port therefore remains within 65535. No checkpoint, data-format, recipe-value, GPU-count, or memory-requirement changes.

Reviewer Notes

PR #471 migrates SGLang to 0.5.19 and removes the derived-port cap while renaming CUDA-graph fields. If it merges first, this branch should be rebased: the 0.5.12-specific config hunk and wording become obsolete, while the helper inlining and baseline/exception documentation still apply.

AI-assisted implementation; the submitter reviewed the full diff. Duplicate-work review found #471's version-migration overlap described above, but no open PR covering the #392 helper/documentation follow-up.

Checklist

• I reviewed the changed code and removed unrelated/generated artifacts.
• I updated tests, docs, and configs where needed, or explained why not.

[CjhHa1]

Superseded by the rebased #471: the helper inlining and documentation cleanup are now included there, while the 0.5.12-specific gRPC port correction is obsolete under the 0.5.19 migration.