R3 gate #21: int refinement overflow proven parametric

[briansrls]

Summary

Strengthens the R3 gate #21 receipt for int_refinement_overflow_proven_parametric by extending the integration coverage for fixed-width integer overflow through the shared MagnitudeOutOfRange path. The receipt now covers additional signed/unsigned width refinements, including Int64, representable Int128::MAX + 1, upper UInt64, and the existing UInt128 lower-bound case.

This is a test-harness receipt change only; no substrate or compiler runtime behavior is changed.

P5 Receipt

P5 explicit deferral receipt: this PR expands an existing hand-authored v3 Rust integration test under src/v3/compiler/tests/integration/int_literal_cardinality_test.rs without adding a new SG-0 path. Lane = T-PB-B / T-Tests-As-Data-Completeness. Concrete ROADMAP row = ROADMAP.md §"Release R1 Program" / "Hand-Rust census" row, which states that the test subset of the SG-0 census migrates to .dag TestClaim declarations and trends to zero Rust-authored tests. This PR keeps the receipt in the existing hand-Rust harness because gate #21 needs executable coverage before the Cluster M / gate #84 bulk migration lands.

SG-0 hand-path delta: 0 (no edits to src/v3/compiler/tests/integration/sg0_census_test.rs; no new hand-authored test path added).

Test plan

• cargo fmt -p v3-compiler — passed
• cargo test -p v3-compiler --test integration int_refinement_overflow_is_proven_parametric_for_representable_widths -- --nocapture — passed on BuildBuddy

[briansrls]

Addressed the P5 receipt finding by replacing the dashboard-template PR body with a concrete hand-Rust deferral receipt: T-PB-B / T-Tests-As-Data-Completeness, ROADMAP.md Hand-Rust census row, plus SG-0 hand-path delta: 0. No code change was needed for this review item. — sent from witty-dove-427

[briansrls]

Review metadata

• Provider / model: codex / unknown
• Commit: 433fa712 · Trigger: schedule
• Thinking: 141s wall

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✅ The test-only expansion looks scoped and clean; it exercises the shared MagnitudeOutOfRange path for Int64, Int128, and UInt64 upper-bound overflow without adding substrate state.