Add List panel (session 9, fifteenth feature)

Renders a naming-scheme-style expression per loaded file via the same
render_expression engine the Rename panel's live preview uses, fed by
the same local guess_episode/guess_movie/guess_release_info matching
Filter already uses. Copy List and Export to File... (a new
export_text_list Tauri command - the only new backend surface this
feature needed) round it out. Closes out all six original sidebar
panels as real screens.

src-tauri/src/lib.rs

@@ -2,6 +2,7 @@ mod cli;
 mod episodes;
 mod files;
 mod history;
+mod list;
 mod metadata;
 mod presets;
 mod settings;
@@ -121,6 +122,7 @@ pub fn run() {
             sfv::compute_checksums,
             sfv::save_checksum_file,
             sfv::verify_checksum_file,
+            list::export_text_list,
             history::list_rename_history,
             history::undo_rename_batch,
             presets::list_presets,

src-tauri/src/list.rs

@@ -0,0 +1,61 @@
+//! The Tauri-facing side of the List panel: exports a set of already-rendered text
+//! lines (one per loaded file) to a plain text file the user picks via a native
+//! "Save File" dialog. This is the *only* new Tauri surface List needs - matching
+//! each file against local metadata and rendering a naming-scheme-style expression
+//! per file both reuse commands that already exist: `guess_episode`/`guess_movie`/
+//! `guess_release_info` (the same local guessers the Rename panel's "Match" and the
+//! Filter panel's scan already call) and `render_expression` (the same engine the
+//! Rename panel's live preview already calls). The frontend builds the final,
+//! newline-joined text; this module's only job is writing it to a file the user
+//! chooses, the same async native-dialog pattern `sfv::save_checksum_file` uses.
+
+use tauri::AppHandle;
+use tauri_plugin_dialog::DialogExt;
+
+/// The `.txt`-suffixed file name to default the Save dialog to.
+fn default_export_filename(default_name: &str) -> String {
+    format!("{default_name}.txt")
+}
+
+/// Opens a native "Save File" dialog defaulted to `<default_name>.txt`, and if the
+/// user doesn't cancel, writes `content` there verbatim (already newline-joined by
+/// the frontend, one rendered line per loaded file). Returns the saved path, or
+/// `None` if the user cancelled the dialog (not an error) - same shape as
+/// `sfv::save_checksum_file`.
+#[tauri::command]
+pub async fn export_text_list(app: AppHandle, default_name: String, content: String) -> Result<Option<String>, String> {
+    let (tx, rx) = tokio::sync::oneshot::channel();
+    app.dialog()
+        .file()
+        .set_file_name(default_export_filename(&default_name))
+        .save_file(move |result| {
+            let _ = tx.send(result);
+        });
+    let chosen = rx.await.map_err(|e| e.to_string())?;
+
+    let Some(file_path) = chosen else {
+        return Ok(None);
+    };
+    let path = file_path.into_path().map_err(|e| e.to_string())?;
+
+    tauri::async_runtime::spawn_blocking({
+        let path = path.clone();
+        move || std::fs::write(&path, content)
+    })
+    .await
+    .map_err(|e| e.to_string())?
+    .map_err(|e| e.to_string())?;
+
+    Ok(Some(path.to_string_lossy().to_string()))
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn default_export_filename_appends_txt_extension() {
+        assert_eq!(default_export_filename("my-list"), "my-list.txt");
+        assert_eq!(default_export_filename(""), ".txt");
+    }
+}