Add unattended end-to-end self-test mode for the production webview

VOICED_SELFTEST_OUT runs the Diagnostics checks plus an issue, archive,
export (searchable, flattened, re-render), cancel and archive-immutability
flow through the real IPC, writes a JSON report and exits. Inert without
the variable; doubles as the per-release gate on installed builds.

src-tauri/src/lib.rs

@@ -2,6 +2,7 @@ mod commands;
 mod db;
 mod gst;
 mod models;
+mod selftest;
 
 use rusqlite::Connection;
 use std::path::{Path, PathBuf};
@@ -135,6 +136,8 @@ pub fn run() {
             commands::files::get_last_export_dir,
             commands::files::reveal_in_folder,
             commands::files::open_file,
+            selftest::selftest_config,
+            selftest::selftest_report,
         ])
         .run(tauri::generate_context!());
 

src-tauri/src/selftest.rs

@@ -0,0 +1,46 @@
+//! Unattended end-to-end self-test hook. Inert unless `VOICED_SELFTEST_OUT` is set: the webview asks
+//! for the report path at startup, runs its checks and hands the JSON back, and the process exits with
+//! the verdict. This is the release gate that proves the real webview works, which Node tests cannot.
+use std::io::Write;
+use std::path::{Path, PathBuf};
+
+const ENV_VAR: &str = "VOICED_SELFTEST_OUT";
+
+fn configured_path() -> Option<PathBuf> {
+    std::env::var_os(ENV_VAR).filter(|v| !v.is_empty()).map(PathBuf::from)
+}
+
+fn write_report(path: &Path, json: &str) -> Result<(), String> {
+    if let Some(parent) = path.parent() {
+        std::fs::create_dir_all(parent).map_err(|e| format!("Could not create {}: {e}", parent.display()))?;
+    }
+    let mut file = std::fs::File::create(path).map_err(|e| format!("Could not write the report: {e}"))?;
+    file.write_all(json.as_bytes())
+        .and_then(|()| file.sync_all())
+        .map_err(|e| format!("Could not write the report: {e}"))
+}
+
+#[tauri::command]
+pub fn selftest_config() -> Option<String> {
+    configured_path().map(|p| p.to_string_lossy().into_owned())
+}
+
+#[tauri::command]
+pub fn selftest_report(json: String, ok: bool) -> Result<(), String> {
+    let path = configured_path().ok_or_else(|| "The self-test is not enabled".to_string())?;
+    write_report(&path, &json)?;
+    std::process::exit(if ok { 0 } else { 1 });
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn writes_the_report_creating_folders() {
+        let dir = tempfile::tempdir().unwrap();
+        let path = dir.path().join("a/b/report.json");
+        write_report(&path, "{\"ok\":true}").unwrap();
+        assert_eq!(std::fs::read_to_string(&path).unwrap(), "{\"ok\":true}");
+    }
+}