Fix suggestions on current PowerShell 7 releases

[RudySource]

Summary

• enable the native Dirgo predictor on PowerShell 7.4, 7.5, and 7.6
• keep the PSReadLine 2.2.2 minimum and PowerShell 7 major-version boundary
• add checksum-pinned Windows smoke coverage across all three supported PowerShell release lines
• publish consistent 0.8.4 version metadata and documentation

Verification

• scripts/release-preflight.sh --require-fish
• cargo check --locked --target x86_64-pc-windows-msvc --all-targets --all-features
• real native predictor smoke on portable PowerShell 7.4.19 and 7.6.4
• Windows CI matrix: PowerShell 7.4.19, 7.5.10, and 7.6.4