docs: align the cron, teammate-pane and TUI comments with the paste

- cron resolvePrompt(): give the reason the rest of the cron docs give (the
  submit check cannot recognise a multi-line paste; in paste mode the newlines
  reach the CLI as keys) instead of the old one about writeViaMux fusing lines.
- sendInputToPane(): it types with send-keys -l and strips line breaks, so it
  no longer uses "the same approach as sendInput()".
- TUI client: newlines become spaces (the docstring said stripped), and the
  test name no longer cites "multi-line breaks Ink".

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

src/cron/cron-service.ts

@@ -536,11 +536,11 @@ export class CronService {
   }
 
   /**
-   * Resolves the prompt text and enforces the single-line constraint: prompt
-   * delivery rides writeViaMux/PTY writes where a newline is Enter, so a
-   * multi-line prompt would be silently corrupted (typed mode fuses lines,
-   * paste mode submits the first line and dribbles the rest in as separate
-   * messages). Rather than mangle an unattended agent's instructions, fail the
+   * Resolves the prompt text and enforces the single-line constraint: a job
+   * fires unattended, and the submit check that re-presses an ignored Enter
+   * cannot recognise a multi-line paste in the composer (typed mode), so a
+   * stranded prompt would go unnoticed; in paste mode the newlines reach the
+   * CLI as keys. Rather than risk an unattended agent's instructions, fail the
    * run with a clear error. A prompt FILE may end with trailing newline(s)
    * (every editor writes one) — those are stripped before the check.
    */