fix(javascript): underflow tiny float16 magnitudes to signed zero - #4004
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toFloat16Bits shifted the significand by (-1 - exponent) for subnormals; for magnitudes below 2^-32 the shift count reaches 32 and JS masks it with & 31, leaving garbage bits (1e-10 encoded as -15352, 1e-11 as NaN). Underflow values below the smallest float16 subnormal to signed zero.
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Why?
toFloat16Bits shifted the significand by (-1 - exponent) for subnormals; for magnitudes below 2^-32 the shift count reaches 32 and JS masks it with & 31, leaving garbage bits (1e-10 encoded as -15352, 1e-11 as NaN). Underflow values below the smallest float16 subnormal to signed zero.
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yes/noyes, I included a completed AI Contribution Checklist in this PR description and the requiredAI Usage Disclosure.yes, my PR description includes the requiredai_reviewsummary and screenshot evidence or equivalent persisted links of the final clean AI review results from both fresh reviewers described inAI_POLICY.md, the Fory-guided reviewer and the independent general reviewer, on the current PR diff or current HEAD after the latest code changes.Does this PR introduce any user-facing change?
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