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/backend/docker/bottle_state.py

@@ -109,6 +109,8 @@ class BottleMetadata:
     # for state dirs written before PRD 0040; callers default to "docker"
     # for backward compatibility.
     backend: str = ""
+    label: str = ""
+    color: str = ""
 
 
 def metadata_path(identity: str) -> Path:
@@ -144,6 +146,8 @@ def read_metadata(identity: str) -> BottleMetadata | None:
         started_at=str(raw_typed.get("started_at", "")),
         compose_project=str(raw_typed.get("compose_project", "")),
         backend=str(raw_typed.get("backend", "")),
+        label=str(raw_typed.get("label", "")),
+        color=str(raw_typed.get("color", "")),
     )