fix: prevent arrow keys from inserting escape sequences as text (#493)

Arrow keys produce `^[[D`/`^[[C` instead of moving the cursor when event
loop latency causes the StdinBuffer to split escape sequences.

Three layered fixes:

1. Increase StdinBuffer timeout from 10ms to 50ms (matches xterm default)
   so split escape sequences are reassembled even under load.

2. Clean up stale readline listeners after @clack/prompts onboarding —
   readline.emitKeypressEvents() leaves a permanent data listener that
   is unnecessary for the TUI.

3. Guard in editor against CSI remnants: if a split still occurs, reject
   text matching navigation escape patterns ([A-F, [H, [Z, [n~) instead
   of inserting them as characters.

Closes #493

packages/pi-tui/src/components/editor.ts

@@ -730,8 +730,17 @@ export class Editor implements Component, Focusable {
 			return;
 		}
 
-		// Regular characters
+		// Regular characters — reject partial escape sequence remnants that can
+		// occur when event loop latency causes the StdinBuffer to split an escape
+		// sequence (e.g. \x1b flushed as ESC, then "[D" arrives as text).
 		if (data.charCodeAt(0) >= 32) {
+			if (data[0] === "[" && data.length >= 2 && data.length <= 8) {
+				const last = data[data.length - 1]!;
+				// CSI navigation remnants: [A-F (arrows/home/end), [H, [Z (shift-tab), [<n>~ (func keys)
+				if (/^[A-FHZ]$/.test(last) || last === "~") {
+					return; // Drop CSI remnant (e.g. "[D", "[C", "[5~")
+				}
+			}
 			this.insertCharacter(data);
 		}
 	}

packages/pi-tui/src/terminal.ts

@@ -112,7 +112,10 @@ export class ProcessTerminal implements Terminal {
 	 * to handle the case where the response arrives split across multiple events.
 	 */
 	private setupStdinBuffer(): void {
-		this.stdinBuffer = new StdinBuffer({ timeout: 10 });
+		// 50ms matches xterm's default escapeCodeTimeout and gives enough headroom
+		// for escape sequences that arrive split across multiple stdin data events
+		// (e.g. \x1b arriving separately from [D due to event loop latency).
+		this.stdinBuffer = new StdinBuffer({ timeout: 50 });
 
 		// Kitty protocol response pattern: \x1b[?<flags>u
 		const kittyResponsePattern = /^\x1b\[\?(\d+)u$/;

src/cli.ts

@@ -137,6 +137,15 @@ migratePiCredentials(authStorage)
 // Run onboarding wizard on first launch (no LLM provider configured)
 if (!isPrintMode && shouldRunOnboarding(authStorage)) {
   await runOnboarding(authStorage)
+
+  // Clean up stdin state left by @clack/prompts.
+  // readline.emitKeypressEvents() adds a permanent data listener and
+  // readline.createInterface() may leave stdin paused. Remove stale
+  // listeners and pause stdin so the TUI can start with a clean slate.
+  process.stdin.removeAllListeners('data')
+  process.stdin.removeAllListeners('keypress')
+  if (process.stdin.setRawMode) process.stdin.setRawMode(false)
+  process.stdin.pause()
 }
 
 // Non-blocking update check — runs at most once per 24h, fire-and-forget