feat(team): team enhancements, subagentModel, parallel tool exec

Port the agent-team enhancement layer onto upstream/main so the model
can spin up coordinated sub-agent teams for parallel work.

subagentModel config wiring (fix):
- Add subagent_model field to RuntimeFeatureConfig + RuntimeConfig::subagent_model()
  accessor so the subagentModel setting (already validated by config_validate.rs)
  is now actually read and stored.
- Agent tool's resolve_agent_model falls back to subagentModel from config
  when no explicit model is passed.

Provider namespace separation:
- New 'custom-openai' provider kind with dedicated env vars
  (CLAWCUSTOMOPENAI_API_KEY / CLAWCUSTOMOPENAI_BASE_URL)
- /setup wizard saves kind: 'custom-openai' for option 5
- Bare model name normalized to 'custom/' prefix to avoid proxy 404s
- Sub-agents inherit /setup-saved provider config via inject_config_as_env_fallbacks

Parallel tool execution:
- Override execute_batch to classify read-only tools as parallel-safe
  and run them concurrently via std::thread::scope
- Results return in original model order

Team coordination layer:
- AgentMessage, TaskClaim, TeamStatus tools + shared mailbox directory
- Mode presets (tiny/1x ... mega/6x) + enriched TeamCreate/Agent descriptions
- Background team watcher
- /team slash command: on/off/status/toggle

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

rust/crates/tools/src/lane_completion.rs

@@ -116,6 +116,8 @@ mod tests {
             lane_events: vec![],
             derived_state: "working".to_string(),
             current_blocker: None,
+            team_id: None,
+            task_id: None,
             error: None,
         }
     }