docs(changelog): cut v0.5.0 section

[avrabe]

Summary

Promotes the CHANGELOG [Unreleased] placeholder to [0.5.0] ahead of tagging v0.5.0.

Covers the v0.5.0 verification & robustness theme:

• feat(verify): validator pattern — full i32 + i64 op surface (#76) #133 — validator pattern from prototype to production: full i32 + i64 op surface certified by Z3ArmValidator (closes Adopt validator-based verification strategy (CompCert pattern) for i64/f32/f64 proof coverage #76).
• feat(riscv): i64 div/rem (Phase 3) — inline software long division #131 — RV32 i64 div/rem (Phase 3 completes the i64 integer surface).
• fix(opt): ir_to_arm returns Result — panic-free optimized path, fuzz re-gated #132 — panic-free ir_to_arm + pop_i32_unary! macro fix; wasm_ops_lower_or_error re-gated (debt open since v0.3.1).

Once this merges, the v0.5.0 tag is pushed against the merge commit, triggering the release pipeline (binaries + SHA256SUMS + SLSA provenance + cosign signatures).

🤖 Generated with Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

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