Improve package docs, example, and publish workflow

[RockerFlower]

Summary:

• Prepare the package for the 0.2.4 release.
• Replace the reusable pub.dev publish workflow with direct Node 24-compatible publish steps.
• Add fuller public API dartdocs and expand README usage guidance.
• Add a README screenshot for the Wave Generator demo.
• Refresh the example app into an interactive console with live preview, navbar performance metrics, a single Code dialog entry, and copyable code output.
• Clarify RandomConfig as seeded generated colors in docs and the example UI.
• Remove stale generated Flutter web plugin registrant from the example.

Validation:

• fvm flutter analyze
• fvm flutter test
• fvm flutter build web --release from example
• fvm dart pub publish --dry-run reported 0 warnings