fix(bench): reject invalid sample counts before calibration

[bobzhang]

Benchmark sample counts were converted to Int by clearing the high bit, silently changing large UInt counts. A zero count reached calibration and ran callbacks before failing on empty statistics.

Validate the count as 1 through 2147483647 before calibration. Add panic regressions for zero and out-of-range counts, and document the accepted range and Bench type name.

Validation:

• moon check --deny-warn
• moon test bench --target all
• moon info; generated interfaces unchanged

[coveralls]

Coverage Report for CI Build 6629

Coverage increased (+0.001%) to 89.315%

Details

• Coverage increased (+0.001%) from the base build.
• Patch coverage: 2 of 2 lines across 1 file are fully covered (100%).
• No coverage regressions found.

Uncovered Changes

No uncovered changes found.

Coverage Regressions

No coverage regressions found.

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Coverage Stats

Relevant Lines:	18409
Covered Lines:	16442
Line Coverage:	89.32%
Coverage Strength:	273010.75 hits per line

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💛 - Coveralls