fix(tmux): type a single-character submit so a dialog answer selects

Claude Code's and Codex's selection dialogs ignore a bracketed paste, so
after the previous commit a pasted `3` + Enter confirmed the highlighted
option instead of option 3. sendInput() now types a single character with
`send-keys -l` as master did (submitsAsKeys()). One character cannot form
the burst Codex reads as a paste, so the Codex fix is unaffected.

The trailing-`;` escape moves into escapeTmuxTrailingSemicolon() and now
also covers every `send-keys -l` call in sendInput() and
sendInputToPane(); tmux 3.5a types `x;` for `send-keys -l 'x\;'`.

Docs: the @fileoverview lines and orchestrator-loop-architecture.md still
described `send-keys -l`; CLAUDE.md, architecture-invariants.md and
cron-guide.md name the single-character exception.

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

docs/orchestrator-loop-architecture.md

@@ -244,7 +244,7 @@ RalphLoop.tick() → assignTasks()  // OR OrchestratorLoop does its own assignme
 session.sendInput(task.prompt)
   │
   ▼
-writeViaMux() → tmux send-keys -l "prompt..." + Enter
+writeViaMux() → tmux paste-buffer -p (prompt as one bracketed paste) + Enter
   │
   ▼
 Claude CLI receives prompt, executes, outputs results