release: heb-diac-small-1.0

[ronaldtse]

Summary

• publish heb-diac-small-1.0 (fp32): GH Release + models.yaml entry
• parity cer_delta 0.0pp on 1,864 samples (fp32 exact); strict validator gate passed
• ByT5-small student distilled from the s43 teacher: DER 30.37% vs teacher 24.79% (+5.58pp, inside the pre-accepted budget)

Test plan

• CI green
• runtime fetch Model.load("heb-diac-small-1.0") resolves and verifies