chore: upgrade to Node 24 and latest dependencies

[yujiaxu-ops]

Summary

• raise the minimum runtime from Node 20 to Node 24 and compile against ES2024
• upgrade pnpm, TypeScript, tsx, Commander, Sharp, and Zod to their latest stable releases
• align Node types with the Node 24 runtime baseline
• upgrade GitHub Actions and test packaged installs on Node 24 and Node 26
• resolve the open Sharp and esbuild Dependabot alerts

Validation

• pnpm run typecheck
• pnpm test (363 passed)
• pnpm run build
• pnpm pack
• Node 26 CLI startup smoke test
• pnpm audit (no known vulnerabilities)

Compatibility

This intentionally drops Node 20 and Node 22 runtime support; the next release should use a compatibility-signaling version such as 0.2.0.