Capture and grow the user's writing voice from real evidence. Use the first time they set up the skill ("set up my voice"), when they share a piece of writing they like ("this sounds like me", "learn from this", "save this to my voice"), when they reword or reject a draft mid-session, at the end of a writing session, or when they type /voice-capture. Writes to the shared voice profile and sample library (which the writing-style skill reads). The learn half of the voice system; writing-style is the apply half.
