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/tui/tui-client.ts

@@ -704,9 +704,9 @@ export class TuiClient {
    *
    * Two hard rules from CLAUDE.md, both enforced here so no caller can get them
    * wrong: the payload must END with `\r` or the server never issues Enter and
-   * the text sits unsubmitted, and embedded newlines are stripped rather than
-   * sent (the server would paste them as one block, which its submit check
-   * cannot reliably recognise in the composer).
+   * the text sits unsubmitted, and embedded newlines become spaces rather than
+   * being sent (the server would paste them as one block, which its submit
+   * check cannot reliably recognise in the composer).
    * The `clientId`/`seq` pair makes delivery exactly-once, so a retry after a
    * dropped connection cannot type the prompt twice.
    */