fix(tmux): submit text as a bracketed paste so Codex does not swallow Enter

sendInput() typed the text of a text+Enter pair with `send-keys -l` and
sent Enter 50 ms later. Codex detects an unmarked paste from a fast
character burst and folds an Enter inside that window into the paste as a
newline, so the prompt stays in the composer unsubmitted. Measured with
codex-cli 0.162.1 in a throwaway tmux pane: 1505 chars stuck 3/3 as
`[Pasted Content 1506 chars]`, a 98-char line stuck 1/4. SubmitVerifier
re-presses Enter for the short case, but it cannot match the long one: the
composer shows the placeholder instead of the prompt's head.

The text now goes in via set-buffer + `paste-buffer -p -d` (markers only
when the pane requested bracketed paste), followed by the separate Enter as
before. Same pane, same texts: 4/4 and 3/3 submitted. Each send gets its
own named buffer; a paste that fails (pane or server gone) deletes it,
since tmux never trims named buffers on its own.

Also escapes a trailing `;` in the text, which tmux treats as a command
separator (`send-keys -l 'x;'` typed `x`, a lone `;` typed nothing).

sendInputToPane() has no callers in src/ and is left as it was.

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

src/session.ts

@@ -4527,7 +4527,7 @@ export class Session extends EventEmitter {
    *
    * More reliable than direct PTY write for programmatic input, especially
    * with Claude CLI which uses Ink (React for terminals).
-   * Uses tmux `send-keys -l` to inject text + Enter.
+   * Uses tmux to inject the text (one bracketed paste) + Enter.
    *
    * @param data - Input data with optional `\r` for Enter
    * @returns true if input was sent, false if no mux session or PTY