fix: address final review findings (clip reset, codecs, paths, timeline)

Co-authored-by: Cursor <cursoragent@cursor.com>

src-tauri/src/services/clip_exporter.rs

@@ -23,11 +23,20 @@ pub fn build_ffmpeg_args(
             args.extend(["-c".to_string(), "copy".to_string()]);
         }
         CutMode::Precise { format: _ } => {
+            let ext = Path::new(output)
+                .extension()
+                .map(|e| e.to_string_lossy().to_ascii_lowercase())
+                .unwrap_or_default();
+            let (video_codec, audio_codec) = match ext.as_str() {
+                "webm" => ("libvpx-vp9", "libopus"),
+                "mp4" | "mkv" => ("libx264", "aac"),
+                _ => ("libx264", "aac"),
+            };
             args.extend([
                 "-c:v".to_string(),
-                "libx264".to_string(),
+                video_codec.to_string(),
                 "-c:a".to_string(),
-                "aac".to_string(),
+                audio_codec.to_string(),
             ]);
         }
     }
@@ -36,6 +45,20 @@ pub fn build_ffmpeg_args(
     args
 }
 
+pub fn expand_tilde_path(path: &str) -> String {
+    if path == "~" {
+        return dirs::home_dir()
+            .map(|p| p.to_string_lossy().to_string())
+            .unwrap_or_else(|| path.to_string());
+    }
+    if let Some(rest) = path.strip_prefix("~/") {
+        if let Some(home) = dirs::home_dir() {
+            return home.join(rest).to_string_lossy().to_string();
+        }
+    }
+    path.to_string()
+}
+
 pub fn generate_output_path(
     output_dir: &str,
     video_title: &str,
@@ -206,6 +229,18 @@ mod tests {
         let args = build_ffmpeg_args(&clip, "input.mp4", "output.mp4", &mode);
         assert!(args.contains(&"-c:v".to_string()));
         assert!(args.contains(&"libx264".to_string()));
+        assert!(args.contains(&"aac".to_string()));
+
+        let webm_args = build_ffmpeg_args(&clip, "input.mp4", "output.webm", &mode);
+        assert!(webm_args.contains(&"libvpx-vp9".to_string()));
+        assert!(webm_args.contains(&"libopus".to_string()));
+    }
+
+    #[test]
+    fn test_expand_tilde_path() {
+        let expanded = expand_tilde_path("~/Videos");
+        assert!(!expanded.starts_with("~/"));
+        assert!(expanded.ends_with("Videos") || expanded.contains("Videos"));
     }
 
     #[test]