fix(coding-agent): preserve indentation in ANSI-rendered HTML export

HTML div elements collapse whitespace by default, stripping leading
spaces from ANSI-rendered tool output (e.g. JSON code blocks).
Added white-space: pre-wrap to .ansi-line class.

packages/coding-agent/src/core/export-html/template.css

@@ -503,6 +503,10 @@
       display: block;
     }
 
+    .ansi-line {
+      white-space: pre-wrap;
+    }
+
     .tool-images {
     }