feat(agents): named and labelled agents with optional ANSI color

Chunk 1 (schema + storage): BottleSpec, ActiveAgent, and BottleMetadata
gain label and color fields. Both docker and smolmachines backends
persist them to metadata.json on prepare and surface them in
enumerate_active_agents(). AgentProvider.provision_plan() passes
label/color through to the Claude provider, which injects them into
claude.json so claude-code displays the session name and color in its
header. Codex provider accepts and ignores the knobs.

Chunk 2 (curses modal + display): cmd_start presents a two-step curses
modal — first edit the label (first keystroke replaces the pre-fill),
then optionally pick a color. cli list active renders label with ANSI
escape codes when the terminal supports it, falling back to agent_name
when no label is set.

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

bot_bottle/cli/start.py

@@ -80,11 +80,15 @@ def cmd_start(argv: list[str]) -> int:
         if backend_name is None:
             return 0
 
+    label, color = tui.name_color_modal(default_label=agent_name)
+
     spec = BottleSpec(
         manifest=manifest,
         agent_name=agent_name,
         copy_cwd=args.cwd,
         user_cwd=USER_CWD,
+        label=label,
+        color=color,
     )
     return _launch_bottle(
         spec,