fix(suite_C): describe the actual reason a precision level is skipped

[JuhaoLiang1997]

Follow-up to the cleanup in #45. That PR removed the runner-declared quantization-backend gating logic and renamed the obvious skip-reason in the headline print (line 101), but two sibling references to the old strategy were missed:

• The function-level docstring still claimed format selection intersects with runner.SUPPORTED_QUANTIZATIONS and warns on any format the runner doesn't declare.
• The per-format final-summary line printed skipped (backend not in SUPPORTED_QUANTIZATION_BACKENDS) even though the skipped list now only ever holds the other full-precision baseline (e.g. FP16 on Ampere where the hw baseline is BF16).

Rewrite both so the docstring describes today's policy (always include the hw-supported full-precision baseline; dispatch every quantized level; let the inference subprocess decide hardware compatibility) and the skip-reason print matches what actually causes the entry.

The result.json field name precision_levels_skipped is kept — it's a stable schema field already indexed by the leaderboard and used by older results, so the name stays; only the human-readable strings around it are corrected.

No functional change.

Summary

Type of change

• New platform support
• Bug fix (runner, validator, leaderboard, or tooling)
• Suite definition change
• Schema change
• Leaderboard / UI improvement
• Documentation
• Other:

Testing

# Commands used to verify

Checklist

• I have read CONTRIBUTING.md
• My change does not break existing result.json files (or I have explained the migration path)
• If adding a new platform: runner inherits from BenchmarkRunner, produces valid result.json, includes a reference result
• If changing the schema: validate_submission.py updated and all existing results still validate
• If changing the leaderboard generator: leaderboard/generate.py produces correct output on existing results
• I have updated relevant documentation

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