release: safe-ai-skill v1.0.0 (install paths, CI, release automation)

[kauenet]

Brings the real v1.0.0 ship work onto main (PR #1 merged an unpushed/older branch state).

Includes:

• CLI install paths: standalone install.sh (checksum-verified), npm + cargo, README Install section
• scripts/check-versions.sh + CI package-checks, cross-build (all 4 platforms), npm launcher smoke, npm-e2e.yml
• release.yml auto-vendors released binaries into plugins/safe-ai-skill/bin/ via PR
• shim linux-arm64 support + regenerated SHA256SUMS
• npm version 0.1.0 -> 1.0.0; CHANGELOG merged into a single [1.0.0]
• .claude/ gitignored (+ OS/editor/Rust clutter); SECURITY/CHANGELOG reframed general-purpose
• stale solana-new comment removed

After merge: re-tag v1.0.0 on main tip and push to trigger the release.