feat(llm): improve UTF-8 handling in response processing to prevent infinite loops

feat(shell): enhance output capturing by using threads for stdout and stderr
feat(tui): update usage widget to display token counts and provider/model information
refactor(tui): simplify status bar rendering by removing unnecessary token calculations

apps/infrastructure/src/llm/provider.rs

@@ -386,13 +386,22 @@ impl LlmClient {
                 break;
             }
             byte_buf.extend_from_slice(&chunk_buf[..n]);
+
+            // Drain any bytes that are not valid UTF-8 to prevent
+            // infinite loop when a non-UTF-8 sequence is received.
             let valid_len = match std::str::from_utf8(&byte_buf) {
                 Ok(s) => s.len(),
-                Err(e) => e.valid_up_to(),
+                Err(e) => {
+                    let n = e.valid_up_to();
+                    if n == 0 {
+                        // No valid UTF-8 prefix; skip the first byte (likely
+                        // a partial multi-byte sequence or stray byte).
+                        byte_buf.drain(..1);
+                        continue;
+                    }
+                    n
+                }
             };
-            if valid_len == 0 {
-                continue;
-            }
             let text =
                 String::from_utf8_lossy(&byte_buf[..valid_len]).into_owned();
             byte_buf.drain(..valid_len);