fix: Log warning when config file parsing fails

Previously, JSON parsing errors in the config file were silently
swallowed, falling back to defaults without any indication to the user.
Now a warning is logged so users are aware of the issue.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: frankieyan

src/config.mts

@@ -46,7 +46,8 @@ function loadConfig(): Config {
             ...DEFAULT_CONFIG,
             ...parsed,
         }
-    } catch {
+    } catch (error) {
+        console.warn(`Failed to parse config at ${configPath}, using defaults. Error: ${error}`)
         return { ...DEFAULT_CONFIG }
     }
 }