feat(native): register AUMID so Windows rich toasts work (D6)

The WinRT rich toast (reply box P5-41, click-to-open-room P5-35) was inert on
Windows: CreateToastNotifier needs the process under an AppUserModelID mapped to
a Start-Menu shortcut, and none was registered — so it errored and silently fell
back to the plain plugin toast.

New native/aumid.rs (Windows-only; no-op elsewhere), called first in
native::setup: (1) SetCurrentProcessExplicitAppUserModelID("LotusGuild.LotusChat"),
(2) install/refresh a Start-Menu "Lotus Chat.lnk" carrying PKEY_AppUserModel_ID,
reusing jumplist.rs's IShellLinkW + IPropertyStore + PROPVARIANT + IPersistFile
pattern (best-effort; failures logged + swallowed). toast.rs now binds the
notifier via CreateToastNotifierWithId(AUMID).

CI-compile-only (windows runner); runtime needs a Windows build to confirm the
toast shows a reply box + opens the room. windows-crate 0.61 symbol assumptions
(IPersistFile, SetCurrentProcessExplicitAppUserModelID, PROPERTYKEY,
GUID::from_u128, CreateToastNotifierWithId) validated by CI — all mirror existing
jumplist.rs usage where possible.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src-tauri/src/native/aumid.rs

@@ -0,0 +1,111 @@
+//! P5-41 / P5-35 — Register an AppUserModelID (AUMID) so the WinRT rich toasts in
+//! `toast.rs` actually work on Windows.
+//!
+//! `ToastNotificationManager::CreateToastNotifierWithId` (and the ambient
+//! `CreateToastNotifier`) require the process to run under an AUMID that maps to a
+//! Start-Menu shortcut carrying `System.AppUserModel.ID`. An unpackaged Win32 app
+//! (our NSIS build) has none by default, so `Show()` errored and the rich toast
+//! (reply box + click-to-open-room) silently fell back to the plain plugin toast.
+//!
+//! On startup we (1) advertise the AUMID for this process and (2) install/refresh
+//! a Start-Menu `.lnk` (same name → overwrites the installer's, no duplicate)
+//! carrying the AUMID. Reuses the `IShellLinkW` + `IPropertyStore` + `PROPVARIANT`
+//! pattern proven in `jumplist.rs`. Best-effort: any failure is logged and
+//! swallowed (the toast just keeps falling back, as before — never crash boot).
+//!
+//! Non-Windows: a no-op.
+
+use tauri::AppHandle;
+
+/// The AUMID this process advertises and that the Start-Menu shortcut carries.
+/// `toast.rs` binds the toast notifier to it via `CreateToastNotifierWithId`.
+pub const APP_USER_MODEL_ID: &str = "LotusGuild.LotusChat";
+
+#[cfg(target_os = "windows")]
+pub fn ensure_app_user_model_id(_app: &AppHandle) {
+    use std::os::windows::ffi::OsStrExt;
+    use windows::core::{Interface, GUID, HSTRING, PCWSTR};
+    use windows::Win32::System::Com::{
+        CoCreateInstance, CoInitializeEx, CoUninitialize, IPersistFile,
+        StructuredStorage::PROPVARIANT, CLSCTX_INPROC_SERVER, COINIT_APARTMENTTHREADED,
+    };
+    use windows::Win32::UI::Shell::{
+        PropertiesSystem::{IPropertyStore, PROPERTYKEY},
+        IShellLinkW, SetCurrentProcessExplicitAppUserModelID, ShellLink,
+    };
+
+    // 1. Advertise the AUMID for this process (must happen before any toast fires).
+    if let Err(e) =
+        unsafe { SetCurrentProcessExplicitAppUserModelID(&HSTRING::from(APP_USER_MODEL_ID)) }
+    {
+        eprintln!("aumid: SetCurrentProcessExplicitAppUserModelID failed: {e}");
+    }
+
+    // 2. Install/refresh the Start-Menu shortcut carrying the AUMID so Action
+    //    Center attributes toasts to "Lotus Chat". Path via %APPDATA% (avoids the
+    //    SHGetKnownFolderPath free-mem dance); dir already exists for installed apps.
+    let appdata = match std::env::var_os("APPDATA") {
+        Some(v) => v,
+        None => return,
+    };
+    let mut lnk = std::path::PathBuf::from(appdata);
+    lnk.push(r"Microsoft\Windows\Start Menu\Programs");
+    let _ = std::fs::create_dir_all(&lnk);
+    lnk.push("Lotus Chat.lnk");
+
+    let exe = match std::env::current_exe() {
+        Ok(p) => p,
+        Err(_) => return,
+    };
+    let exe_wide: Vec<u16> = exe
+        .as_os_str()
+        .encode_wide()
+        .chain(std::iter::once(0))
+        .collect();
+    let lnk_wide: Vec<u16> = lnk
+        .as_os_str()
+        .encode_wide()
+        .chain(std::iter::once(0))
+        .collect();
+
+    // PKEY_AppUserModel_ID = {9F4C2855-9F79-4B39-A8D0-E1D42DE1D5F3}, pid 5.
+    // Constructed inline so we don't depend on the const's crate module path.
+    const PKEY_APP_USER_MODEL_ID: PROPERTYKEY = PROPERTYKEY {
+        fmtid: GUID::from_u128(0x9F4C2855_9F79_4B39_A8D0_E1D42DE1D5F3),
+        pid: 5,
+    };
+
+    // STA apartment for the shell link objects, mirroring jumplist.rs. All COM
+    // interfaces are dropped before CoUninitialize.
+    let hr = unsafe { CoInitializeEx(None, COINIT_APARTMENTTHREADED) };
+    let result = (|| -> windows::core::Result<()> {
+        unsafe {
+            let link: IShellLinkW = CoCreateInstance(&ShellLink, None, CLSCTX_INPROC_SERVER)?;
+            link.SetPath(PCWSTR(exe_wide.as_ptr()))?;
+            link.SetIconLocation(PCWSTR(exe_wide.as_ptr()), 0)?;
+
+            // Stamp the AUMID onto the link's property store (VT_LPWSTR, exactly
+            // like PKEY_Title in jumplist.rs).
+            let store: IPropertyStore = link.cast()?;
+            let value = PROPVARIANT::from(APP_USER_MODEL_ID);
+            store.SetValue(&PKEY_APP_USER_MODEL_ID, &value)?;
+            store.Commit()?;
+
+            // Persist the .lnk to the Start-Menu Programs folder.
+            let persist: IPersistFile = link.cast()?;
+            // fremember is a Win32 BOOL (not bool); `.into()` uses From<bool>.
+            persist.Save(PCWSTR(lnk_wide.as_ptr()), true.into())?;
+            Ok(())
+        }
+    })();
+
+    if hr.is_ok() {
+        unsafe { CoUninitialize() };
+    }
+    if let Err(e) = result {
+        eprintln!("aumid: failed to install Start-Menu shortcut: {e}");
+    }
+}
+
+#[cfg(not(target_os = "windows"))]
+pub fn ensure_app_user_model_id(_app: &AppHandle) {}

src-tauri/src/native/mod.rs

@@ -8,6 +8,7 @@
 
 use tauri::{AppHandle, Manager};
 
+pub mod aumid;
 pub mod chrome;
 pub mod focus_assist;
 pub mod jumplist;
@@ -34,6 +35,9 @@ pub fn emit_to_web(app: &AppHandle, event: &str, detail_json: &str) {
 /// listeners or managed state get initialized here. (jumplist/chrome are
 /// command-only and need no setup.)
 pub fn setup(app: &AppHandle) -> tauri::Result<()> {
+    // Register the AUMID + Start-Menu shortcut FIRST so the WinRT rich toast can
+    // create its notifier (before any notification path fires). Best-effort.
+    aumid::ensure_app_user_model_id(app);
     power::setup(app)?;
     thumbbar::setup(app)?;
     smtc::setup(app)?;

src-tauri/src/native/toast.rs

@@ -224,8 +224,11 @@ fn show_windows_toast(
         }
     }
 
-    // No AUMID argument: relies on the process AppUserModelID (see module note).
+    // Bind the notifier to our registered AUMID (native::aumid) so it resolves to
-    let notifier = ToastNotificationManager::CreateToastNotifier()?;
+    // the "Lotus Chat" Start-Menu shortcut rather than an ambient/absent default.
+    let notifier = ToastNotificationManager::CreateToastNotifierWithId(&HSTRING::from(
+        crate::native::aumid::APP_USER_MODEL_ID,
+    ))?;
     notifier.Show(&toast)?;
 
     Ok(())