Tryst::CommandInterceptors

Registry of per-Tk-widget-type interceptors that App#command consults before falling back to its own generic handling. Each interceptor is a labeled block registered under a widget type string (the same strings used in WIDGET_COMMANDS); App#command looks up the type for the path it was given (see App#record_widget_type) and tries every interceptor registered for that type.

An interceptor block receives (app, path, args, kwargs) and must return nil if this call isn't its concern - App#raw_command's Tcl results are always Strings, never nil, so nil is an unambiguous "not mine" sentinel - or the Tcl result if it handled the call itself (typically by calling App#raw_command internally).

Multiple widget types can share the same interceptor logic by registering the same block under each type. label is what #command reports if two DIFFERENT interceptors both claim the same call for the same type - it raises AmbiguousCommandError naming both labels rather than silently picking one, so whoever's debugging can tell which interceptors collided.

Class-level (one registry for the whole process, like ruby-tryst's) - registrations are meant to be permanent, load-time declarations (the built-in menu/tag/canvas interceptors, in later tasks, register themselves once when their files are required), not per-App state.