refactor: split pilot architecture

Remove the obsolete dashboard now that Langfuse is the analytics surface.\nIntroduce focused transport, model, and configuration modules while preserving the ai_review facade, and document the current runtime architecture.

pilot/README-langfuse.md

@@ -21,7 +21,7 @@ and lands on the trace's `environment`:
 | `headroom/MiniMax-M2.7`     | `ollama`    |
 | `vllm-qwen38/qwen3.8-27b`   | `ollama`    |
 
-Langfuse takes an environment selector on every dashboard, filter and cost
+Langfuse takes an environment selector on every view, filter and cost
 breakdown, so the two spend stories stay separate inside one project — one key
 pair to rotate instead of two. Tags carry the finer cut:
 `provider:headroom`, `model:<bare>`, `engine:opencode`, `repo:<owner/name>`,
@@ -56,11 +56,11 @@ A model that costs nothing through the headroom proxy is priced against a
 **comparison target** instead: basis `equivalent:<target>`. That covers the
 models absent from `PRICES` (`MiniMax-M2.7` — which is what the webhook
 actually runs — and `glm-5.2:cloud`) as well as entries priced at all zeros
-(the self-hosted vLLM `qwen3.8-27b`). Without this the dashboard would be a
+(the self-hosted vLLM `qwen3.8-27b`). Without this Langfuse would show a
 flat $0.00 line, since the pilot's own path is free.
 
-The target follows the same precedence as the review body, so the PR and the
-dashboard never disagree:
+The target follows the same precedence as the review body, so the PR and
+Langfuse never disagree:
 
     .pr-review.json:cost_target  >  PRAGENT_PRICE_TARGET  >  claude-sonnet-5