Polish examples and docs

[writeameer]

Summary

• Refresh example READMEs and comments to match the current forge.Config, Ask, and LastText API
• Remove stale hello-world references to old provider helper files and constructor names
• Add chat-console to the root README example list
• Update design docs for the current Go version and remove orchestration-oriented future scope
• Replace decorative arrows/dashes in code/docs where they were only stylistic

Verification

• go vet ./...
• go test ./...
• _examples/hello-world: go vet ./... and go test ./...
• _examples/calculator: go vet ./... and go test ./...
• _examples/chat-console: go vet ./... and go test ./...