MTP: Add connection management and ptpcamerad handling

Phase 2 implementation:
- Add MtpConnectionManager with global device registry
- Add connect_mtp_device, disconnect_mtp_device, get_mtp_device_info commands
- Add macOS ptpcamerad workaround with ioreg-based detection
- Add PtpcameradDialog with Terminal command and copy button
- Add TypeScript wrappers and event listeners for MTP errors
- Wire up error dialog in main layout

Author: vdavid

apps/desktop/coverage-allowlist.json

@@ -26,6 +26,7 @@
         "icon-cache.ts": { "reason": "Depends on Tauri APIs" },
         "licensing-store.svelte.ts": { "reason": "Depends on Tauri store APIs" },
         "logger.ts": { "reason": "LogTape config, initialization code only" },
+        "mtp/PtpcameradDialog.svelte": { "reason": "UI modal for macOS MTP workaround" },
         "licensing/AboutWindow.svelte": { "reason": "UI component" },
         "licensing/CommercialReminderModal.svelte": { "reason": "UI component" },
         "licensing/ExpirationModal.svelte": { "reason": "UI component" },

apps/desktop/src-tauri/src/commands/mtp.rs

@@ -1,6 +1,7 @@
 //! Tauri commands for MTP (Android device) operations.
 
-use crate::mtp::{self, MtpDeviceInfo};
+use crate::mtp::{self, ConnectedDeviceInfo, MtpConnectionError, MtpDeviceInfo, MtpStorageInfo};
+use tauri::AppHandle;
 
 /// Lists all connected MTP devices.
 ///
@@ -14,3 +15,73 @@ use crate::mtp::{self, MtpDeviceInfo};
 pub fn list_mtp_devices() -> Vec<MtpDeviceInfo> {
     mtp::list_mtp_devices()
 }
+
+/// Connects to an MTP device by ID.
+///
+/// Opens an MTP session to the device and retrieves storage information.
+/// If another process (like ptpcamerad on macOS) has exclusive access,
+/// an `mtp-exclusive-access-error` event is emitted to the frontend.
+///
+/// # Arguments
+///
+/// * `device_id` - The device ID from `list_mtp_devices` (format: "mtp-{bus}-{address}")
+///
+/// # Returns
+///
+/// Information about the connected device including available storages.
+#[tauri::command]
+pub async fn connect_mtp_device(app: AppHandle, device_id: String) -> Result<ConnectedDeviceInfo, MtpConnectionError> {
+    mtp::connection_manager().connect(&device_id, Some(&app)).await
+}
+
+/// Disconnects from an MTP device.
+///
+/// Closes the MTP session gracefully. The device remains available in
+/// `list_mtp_devices` for reconnection.
+///
+/// # Arguments
+///
+/// * `device_id` - The device ID to disconnect from
+#[tauri::command]
+pub async fn disconnect_mtp_device(app: AppHandle, device_id: String) -> Result<(), MtpConnectionError> {
+    mtp::connection_manager().disconnect(&device_id, Some(&app)).await
+}
+
+/// Gets information about a connected MTP device.
+///
+/// Returns device metadata and storage information for a currently connected device.
+/// Returns `None` if the device is not connected.
+///
+/// # Arguments
+///
+/// * `device_id` - The device ID to query
+#[tauri::command]
+pub fn get_mtp_device_info(device_id: String) -> Option<ConnectedDeviceInfo> {
+    mtp::connection_manager().get_device_info(&device_id)
+}
+
+/// Gets the ptpcamerad workaround command for macOS.
+///
+/// Returns the Terminal command that users can run to work around
+/// ptpcamerad blocking MTP device access.
+#[tauri::command]
+pub fn get_ptpcamerad_workaround_command() -> String {
+    mtp::PTPCAMERAD_WORKAROUND_COMMAND.to_string()
+}
+
+/// Gets storage information for all storages on a connected device.
+///
+/// # Arguments
+///
+/// * `device_id` - The connected device ID
+///
+/// # Returns
+///
+/// A vector of storage info, or empty if device is not connected.
+#[tauri::command]
+pub fn get_mtp_storages(device_id: String) -> Vec<MtpStorageInfo> {
+    mtp::connection_manager()
+        .get_device_info(&device_id)
+        .map(|info| info.storages)
+        .unwrap_or_default()
+}

apps/desktop/src-tauri/src/lib.rs

@@ -351,8 +351,28 @@ pub fn run() {
             // MTP commands (macOS only - Android device support)
             #[cfg(target_os = "macos")]
             commands::mtp::list_mtp_devices,
+            #[cfg(target_os = "macos")]
+            commands::mtp::connect_mtp_device,
+            #[cfg(target_os = "macos")]
+            commands::mtp::disconnect_mtp_device,
+            #[cfg(target_os = "macos")]
+            commands::mtp::get_mtp_device_info,
+            #[cfg(target_os = "macos")]
+            commands::mtp::get_ptpcamerad_workaround_command,
+            #[cfg(target_os = "macos")]
+            commands::mtp::get_mtp_storages,
             #[cfg(not(target_os = "macos"))]
             stubs::mtp::list_mtp_devices,
+            #[cfg(not(target_os = "macos"))]
+            stubs::mtp::connect_mtp_device,
+            #[cfg(not(target_os = "macos"))]
+            stubs::mtp::disconnect_mtp_device,
+            #[cfg(not(target_os = "macos"))]
+            stubs::mtp::get_mtp_device_info,
+            #[cfg(not(target_os = "macos"))]
+            stubs::mtp::get_ptpcamerad_workaround_command,
+            #[cfg(not(target_os = "macos"))]
+            stubs::mtp::get_mtp_storages,
             // Volume commands (platform-specific)
             #[cfg(target_os = "macos")]
             commands::volumes::list_volumes,