/**
 * /btw extension — side-channel chat in a floating window
 *
 * Usage: /btw <question>
 *
 * Opens a side-chat window backed by a one-off LLM thread (streamSimple) that
 * sees the current branch context + your questions. Answers stream live into
 * the window and follow-ups can be typed right there — the main agent's
 * context is never touched, no matter how deep the thread goes.
 *
 * From the window (when idle):
 *   enter    send a follow-up
 *   esc      close (streaming: cancel the in-flight answer)
 *   ctrl+p   promote — close and hand the thread to the main agent
 *   ctrl+f   fork — write branch + thread to a new session file and open it:
 *            tmux split (direction from pane width, PI_BTW_SPLIT=h|v to force)
 *            → new Ghostty window (macOS) → clipboard + printed command
 *
 * On close the thread persists with pi.appendEntry() as a custom ENTRY: it
 * renders in the transcript but never participates in the agent's LLM
 * context and never triggers a turn.
 *
 * Why not pi.sendMessage()? Custom MESSAGES participate in LLM context and,
 * when sent while the agent is streaming, are delivered as steer messages —
 * which continues the agent loop with an extra LLM call. Our own context
 * filter then strips the btw message, leaving the conversation ending with an
 * assistant message, which models that reject assistant prefill 400 on.
 */
import type { ExtensionAPI } from '@earendil-works/pi-coding-agent';
export default function (pi: ExtensionAPI): void;