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

flock.go

@@ -144,14 +144,15 @@ func (f *Flock) ask(ctx context.Context, w Watcher, crow, system, prompt string,
 	cctx, cancel := context.WithTimeout(ctx, f.g.CrowTimeout)
 	defer cancel()
 	start := time.Now()
-	text, tokens, err := f.brain.Ask(cctx, system, prompt)
+	var model string
+	text, tokens, err := f.brain.Ask(withModelSlot(cctx, &model), system, prompt)
 	for _, b := range budgets {
 		b.Add(tokens)
 	}
 	if errors.Is(err, context.DeadlineExceeded) {
 		err = fmt.Errorf("%s timed out after %s and was dropped", crow, f.g.CrowTimeout)
 	}
-	e := Event{Kind: "flight", Crow: crow, Tokens: tokens, Ms: time.Since(start).Milliseconds(), Output: text}
+	e := Event{Kind: "flight", Crow: crow, Model: model, Tokens: tokens, Ms: time.Since(start).Milliseconds(), Output: text}
 	if err != nil {
 		e.Error = err.Error()
 	}