Add Chat Completions API support and expand REPL debugging

- Add NearAiChatProvider using /v1/chat/completions endpoint with API key auth
- Add NEARAI_API_KEY and NEARAI_API_MODE config options
- Auto-detect API mode from presence of API key
- Keep existing Responses API (NearAiProvider) for session-based auth
- Fix response parsing to accept input_text/output_text/text content types
- Expand REPL with /help, /debug toggle, colored output
- Better tool status display (dots vs verbose based on debug mode)

Co-Authored-By: Claude Opus 4.5 <[email protected]>

src/main.rs

@@ -142,12 +142,17 @@ async fn main() -> anyhow::Result<()> {
                 }
                 Ok(_) => {
                     let _ = event_tx
-                        .send(AppEvent::ErrorMessage("No models available from API".into()))
+                        .send(AppEvent::ErrorMessage(
+                            "No models available from API".into(),
+                        ))
                         .await;
                 }
                 Err(e) => {
                     let _ = event_tx
-                        .send(AppEvent::ErrorMessage(format!("Failed to fetch models: {}", e)))
+                        .send(AppEvent::ErrorMessage(format!(
+                            "Failed to fetch models: {}",
+                            e
+                        )))
                         .await;
                 }
             }