fix(singlefile): disable CSS stripping and script blocking for full render fidelity

Defaults that were destroying CSS fidelity:
- --remove-unused-styles=true: strips CSS nesting rules (site uses & selector)
  and any rule targeting JS-applied classes
- --remove-alternative-medias=true: deletes @media blocks that don't match
  the capture viewport, breaking responsive layout
- --block-scripts=true: prevents JS from applying classes before CSS snapshot

All three now set to false.

crates/archivr-core/src/downloader/singlefile.rs

@@ -54,6 +54,13 @@ fn save_with(
         .arg(format!("--browser-executable-path={chrome}"))
         .arg("--browser-headless")
         .arg("--browser-wait-until=networkidle2")
+        // Preserve all CSS: single-file's defaults strip rules it considers
+        // "unused" (breaking CSS nesting) and remove @media blocks that don't
+        // match the capture viewport (breaking responsive layout). Allow scripts
+        // to run so JS-applied classes are present when CSS is evaluated.
+        .arg("--remove-unused-styles=false")
+        .arg("--remove-alternative-medias=false")
+        .arg("--block-scripts=false")
         .output()
         .with_context(|| format!("failed to spawn {single_file} process"))?;