The AI chat composer for Compose Multiplatform — a `PromptBar` composable with slash-command autocomplete, @-mentions for files/symbols/contacts, attachment chips with image thumbnails, a unified Send → Sending → Stop button state machine, voice button, prompt template chips, token counter, keyboard shortcuts and a headless `PromptBarState` you can drive from anywhere. Designed for AI chat / LLM apps; pairs naturally with `llm-typewriter`.