Bugfix: Fix SMB paths with accented characters

- macOS sends paths in NFD (decomposed Unicode, for example `a` + `\u{0308}` for `ä`) but SMB servers expect NFC (composed). Paths with accents failed with `STATUS_OBJECT_PATH_NOT_FOUND`.
- NFC-normalize in `SmbVolume::to_smb_path()` using the existing `unicode-normalization` crate.
- Document the SMB auto-upgrade lifecycle in volume `CLAUDE.md`.

Author: vdavid

apps/desktop/src-tauri/src/file_system/volume/CLAUDE.md

@@ -53,6 +53,22 @@ Optional methods default to `Err(VolumeError::NotSupported)` or `false`, so new
 
 `MtpVolume` is called from `tokio::task::spawn_blocking`, so `Handle::block_on` is safe inside its methods. However, `write_from_stream` must collect all chunks **before** entering `block_on` to avoid nested-runtime panics (stream chunks also use `block_on` internally).
 
+## SMB auto-upgrade lifecycle
+
+SMB mounts are automatically upgraded to `SmbVolume` (direct smb2 connection) in two scenarios:
+
+1. **Startup** (`file_system::upgrade_existing_smb_mounts`): Scans registered volumes for `smbfs` type. Waits for mDNS
+   discovery to reach `Active` state (polls every 500ms, up to 15s) because Keychain credentials are keyed by hostname
+   (from mDNS), not IP (from `statfs`). Uses `tauri::async_runtime::spawn` (not `tokio::spawn` — runs during `setup()`
+   before Tokio is fully available). Emits `volumes-changed` after upgrades so the frontend refreshes indicators.
+
+2. **Mount detection** (`volumes/watcher.rs::try_upgrade_smb_mount`): When FSEvents detects a new volume in `/Volumes/`
+   and it's `smbfs`, spawns a background upgrade attempt. By this point mDNS is already active.
+
+Both paths check the `network.directSmbConnection` setting (global `AtomicBool`). Both are best-effort — failures log a
+warning and the volume stays as `LocalPosixVolume`. The "Connect directly" UI action (`upgrade_to_smb_volume` command)
+provides a manual upgrade path.
+
 ## Integration status
 
 `LocalPosixVolume` is wired into the indexing subsystem. `VolumeManager` is actively used.

apps/desktop/src-tauri/src/file_system/volume/smb.rs

@@ -166,13 +166,18 @@ impl SmbVolume {
     ///
     /// The frontend sends paths relative to the volume root (which is the mount path).
     /// smb2 expects paths relative to the share root with `/` separators.
+    /// NFC-normalizes the result because macOS sends NFD (decomposed) paths
+    /// but SMB servers expect NFC (composed). Without this, paths with accented
+    /// characters (like "ä") fail with STATUS_OBJECT_PATH_NOT_FOUND.
     fn to_smb_path(&self, path: &Path) -> String {
+        use unicode_normalization::UnicodeNormalization;
+
         let path_str = path.to_string_lossy();
 
         // Handle paths that start with the mount path (absolute paths from frontend)
         if let Some(relative) = path_str.strip_prefix(self.mount_path.to_string_lossy().as_ref()) {
             let trimmed = relative.trim_start_matches('/');
-            return trimmed.to_string();
+            return trimmed.nfc().collect();
         }
 
         // Handle empty or root paths
@@ -181,7 +186,8 @@ impl SmbVolume {
         }
 
         // Strip leading slash for absolute paths
-        path_str.strip_prefix('/').unwrap_or(&path_str).to_string()
+        let raw = path_str.strip_prefix('/').unwrap_or(&path_str);
+        raw.nfc().collect()
     }
 
     /// Returns the full absolute path for a relative SMB path (under mount point).