Add window-scoped keydown dispatching with per-key signal and
preventDefault options. Use comma operator instead of semicolons
in generated ternary expressions to produce valid JavaScript.
Flatten DatastarConfig struct into Options (DatastarContent, DatastarPath)
and replace datastarHandlerRegistered bool with sync.Once for thread safety.
Allow users to provide their own Datastar.js script (e.g., Datastar Pro
or custom builds) via Via's Options configuration. Adds DatastarConfig
struct with Content ([]byte) and Path (string) fields.
