fix(respawn): send a multi-line update or kickstart prompt as one line

The update and kickstart prompts are textareas in the respawn settings and
the schema accepts line breaks, so a saved config can hold several lines.
Both steps went out through writeViaMux, which used to strip every `\n` and
run the lines together. Since the mux now pastes multi-line text as one
block, a multi-line respawn prompt would have gone out as a multi-line paste,
and the check that re-presses a stranded Enter cannot recognise that paste in
the composer. Respawn runs unattended, the same situation for which cron
keeps rejecting multi-line prompts.

singleLineRespawnPrompt() joins the lines with a space before the write; a
single-line prompt is passed through unchanged. Respawn joins rather than
rejects, so a multi-line config that was accepted before is still sent.

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

src/respawn-controller.ts

@@ -503,6 +503,19 @@ function formatRemainingSeconds(ms: number): number {
   return Math.max(0, Math.ceil(ms / 1000));
 }
 
+/**
+ * A respawn prompt as the one line it is sent as: every run of line breaks, with the
+ * whitespace around it, becomes a single space; a single-line prompt is returned as
+ * is. The config may hold several lines (the settings fields are textareas), but the
+ * steps run unattended through `writeViaMux`, and the check that re-presses a stranded
+ * Enter cannot recognise a multi-line paste in the composer. Cron rejects multi-line
+ * prompts for the same reason; respawn joins them instead, so a saved multi-line
+ * config is still sent rather than refused.
+ */
+export function singleLineRespawnPrompt(prompt: string): string {
+  return prompt.replace(/\s*[\r\n]+\s*/g, ' ');
+}
+
 /** Default configuration values */
 const DEFAULT_CONFIG: RespawnConfig = {
   idleTimeoutMs: 10000, // 10 seconds of no activity after prompt (legacy, still used as fallback)
@@ -1621,7 +1634,7 @@ export class RespawnController extends EventEmitter {
       this.config.interStepDelayMs,
       async () => {
         if (this._state === 'stopped') return;
-        const prompt = this.config.kickstartPrompt!;
+        const prompt = singleLineRespawnPrompt(this.config.kickstartPrompt!);
         this.logAction('command', `Sending kickstart: "${prompt.substring(0, 40)}..."`);
         await this.session.writeViaMux(prompt + '\r'); // \r triggers key.return in Ink/Claude CLI
         // COD-51: stop() may have run during the await; re-check before reviving the
@@ -2826,13 +2839,13 @@ export class RespawnController extends EventEmitter {
 
         // Use RALPH_STATUS RECOMMENDATION if available, otherwise fall back to config
         const statusBlock = this.session.ralphTracker?.lastStatusBlock;
-        let updatePrompt = this.config.updatePrompt;
+        let updatePrompt = singleLineRespawnPrompt(this.config.updatePrompt);
 
         if (statusBlock?.recommendation) {
-          // Append RECOMMENDATION to the update prompt (single-line: the submit check cannot
-          // recognise a multi-line paste in the composer)
+          // Append RECOMMENDATION to the update prompt, on the same single line
+          // (see singleLineRespawnPrompt)
           const rec = statusBlock.recommendation.replace(/\n/g, ' ').substring(0, 200);
-          updatePrompt = `${this.config.updatePrompt} (Claude's last recommendation: ${rec})`;
+          updatePrompt = `${updatePrompt} (Claude's last recommendation: ${rec})`;
           this.logAction('ralph', `Using RECOMMENDATION: ${rec.substring(0, 50)}...`);
         }