fix(core): state integer proofs in sdk/text.ts range constructors

[sapjax]

Problem

The shipped packages/core/sdk/text.ts (v0.9.5, unchanged on main) fails the pinned scriptc 0.0.33 integer-boundary checks — 19 × SC4022/SC4023 errors on every TextRange/TextSelection construction that isn't routed through caretSelectionAt:

sdk/text.ts:79:34 - error SC4023: integer slot 'TextRange.start' (i64) cannot be proven — range failed: the proven range [-Infinity, 9007199254740991] does not fit [-9007199254740991, 9007199254740991] — integrality is provable only within ±(2^53 − 1)
sdk/text.ts:79:63 - error SC4022: integer slot 'TextRange.start' (i64) cannot be proven — wholeness failed: the value may be NaN, which is not a whole number
…

Any TS-core app that imports @native-sdk/core/text — i.e. every app with a text field — fails native build. Note native check stays green: this refusal comes from the external core compiler's integer-boundary proofs, not the NS subset checker, and the repo's external-compiler tests stub scriptc with a fixture, so CI never compiles this module with the real pinned compiler.

Fix

State each offset whole in place, using the module's own established idiom — caretSelectionAt already documents exactly this pattern:

offsets are whole byte offsets by contract, proven in place — range-guarded (an ordered comparison excludes NaN) and stated whole with Math.trunc. A value outside the provable ±(2^53 − 1) window clamps to 0, the same floor every caller's snap already applies.

This extends that form to rangeNormalized, snapTextRange, setTextComposition, and the six delete-* edit paths. No behavior change on reachable values: every internal producer already returns whole, non-negative byte offsets ≤ text length.

Verification

• Reproduced all 19 SC4022/SC4023 errors on an app importing @native-sdk/core/text with the unpatched module; with this patch the same app builds clean (native build, ReleaseFast).
• node --test packages/core/test/text.test.ts — 6/6 pass.
• Differential fuzz vs the unpatched module: 4000 rounds / ~23k applied applyTextInputEvent + clampedInsertEvent calls over random UTF-8 text (multibyte, CRLF, selections, compositions, capacity refusals) — byte-identical states.
• tsc --noEmit --strict clean on the patched module.

Possible follow-up (out of scope here): a CI lane that compiles sdk/text.ts / sdk/events.ts with the real pinned scriptc would catch this class of regression — the current external-compiler tests stub scriptc.

[vercel]

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