OpenRouter crows; log which model answered each flight

- ChatBrain speaks OpenAI-style chat completions (OpenRouter now)
- CROWS_PROVIDER picks anthropic or openrouter; default model
  openrouter/free; CROWS_MODEL overrides
- Flight log records the model that actually answered
- Token budgets fall back to a length estimate if usage is missing
- start.command reads either key from .env

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01UQnSw4RRWp8uqpj3nsnnXF

flightlog.go

@@ -17,6 +17,7 @@ type Event struct {
 	Crow      string    `json:"crow,omitempty"`
 	Mode      string    `json:"mode,omitempty"`
 	TaskType  string    `json:"task_type,omitempty"`
+	Model     string    `json:"model,omitempty"` // which model actually answered (routers vary)
 	Tokens    int       `json:"tokens,omitempty"`
 	Ms        int64     `json:"ms,omitempty"`
 	Verdict   string    `json:"verdict,omitempty"`