Expose Active Encoder Category/Page via OSC

Please add the console's current encoder state (active encoder category and page within it) to the implicit OSC output, the same way active wheels (/eos/out/active/wheel/<n>) and softkeys (/eos/out/softkey/<n>) are already broadcast.

For example: /eos/out/active/wheel/page (or /eos/out/encoder/category + /eos/out/encoder/page), emitted whenever the state changes.

Currently, each /eos/out/active/wheel/<n> message carries the parameter's category as an integer argument, and all active wheels are re-sent on selection changes but nothing is emitted when the encoder page or category buttons are pressed. An external display (lighthack-style) can only figure out the current page after an event, by waiting for a wheel's value to change and calculating which page contains it. Until something physically moves, a companion device cannot know what the console's encoders are currently mapped to.

The use case is a display device for my programming wing's encoder wheels, because I often grab the wrong param without realizing.