docs: add community benchmark evidence workflow

[AIwork4me]

Summary

• add a lightweight workflow for submitting independent AMD GPU benchmark evidence
• align the Hardware Matrix with the central ROCmDoc producer-evidence / platform-review model
• add the existing Windows-HIP gfx1151 pipeline and VLM benchmark results
• fix stale reproducibility links and benchmark-description inconsistencies

Scope

This PR does not add the pending external Linux gfx1151 result to the Hardware Matrix. External results require finalized immutable evidence before inclusion.

It does not promote legacy badges, assign central platform-review outcomes, or introduce a new trust taxonomy.

Raw predictions remain optional for community submissions.

Validation

• pytest: 177 passed
• scripts/check_repo.py: clean
• ROCmDoc conformance: CONFORMANT
• git diff --cached --check: passed

Notes

The existing local results/omnidocbench/v16/windows-hip-repro-pipeline/ directory is unrelated and is intentionally not included in this PR.