feat(terminal): tint terminal background per agent color

Add backend-agnostic terminal color support via OSC escape sequences:
- New backend/terminal.py with palette_printf() and exec_shell_script()
  shared by both Docker and smolmachines bottle backends
- Emits OSC 4 (indexed palette) + OSC 11 (default background tint)
  before launching; resets both on agent exit via OSC 104/111
- OSC 11 background tint is visible even when the TUI uses true/24-bit
  colors (which bypass the palette), as Codex does for its chrome
- Fix Codex [tui] config: status_line=["model-with-reasoning"],
  theme="ansi" (dark-ansi and cwd/directory were invalid identifiers)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

bot_bottle/backend/docker/launch.py

@@ -176,6 +176,7 @@ def launch(
             agent_command=plan.agent_command,
             agent_prompt_mode=plan.agent_prompt_mode,
             terminal_title=plan.spec.label or plan.spec.agent_name,
+            terminal_color=plan.spec.color,
         )
         bottle.prompt_path = provision(plan, bottle)