feat(drive): remove create_home_folder

remove create_home_folder() & ensure_home_folder()

    now: on_user_created() and on_user_login both() call provision_if_needed()
    which calls **create_personal_drive_atomic()**

    add a helper to find Personal drive for a user and also it's root directorry

src/domain/repositories/drive_repository.rs

@@ -88,6 +88,30 @@ pub trait DriveRepository: Send + Sync + 'static {
         user_id: Uuid,
     ) -> Result<DriveWithRootName, DriveRepositoryError>;
 
+    /// Canonical "what is this user's home root folder id?" lookup.
+    ///
+    /// Returns `Some(uuid)` for any internal user with a default personal
+    /// drive (the lifecycle hook provisions one at registration), and
+    /// `None` for users who have no default drive (external users; users
+    /// created before the hook existed). The id identifies the user's
+    /// home **by drive ownership** (`default_for_user == user_id`),
+    /// never by folder name — users can rename their home, so any code
+    /// that wants to ask "is this folder the user's home?" must compare
+    /// folder ids, not names.
+    ///
+    /// Storage errors (DB unreachable, etc.) bubble up as `Err`; the
+    /// "user simply has no home" case is `Ok(None)`, not an error.
+    async fn home_root_folder_id_for(
+        &self,
+        user_id: Uuid,
+    ) -> Result<Option<Uuid>, DriveRepositoryError> {
+        match self.find_default_for_user(user_id).await {
+            Ok(d) => Ok(Some(d.drive.root_folder_id)),
+            Err(DriveRepositoryError::NotFound(_)) => Ok(None),
+            Err(e) => Err(e),
+        }
+    }
+
     /// List drives the caller can read, resolved via `role_grants` for
     /// `resource_type='drive'`. The caller's group memberships are
     /// expanded by the engine's `subject_match_set`; that expanded set
@@ -110,3 +134,40 @@ impl DriveKind {
         DriveKind::parse(s).ok_or_else(|| DriveRepositoryError::InvalidKind(s.to_owned()))
     }
 }
+
+/// Locate the user's home root folder within a generic list of items,
+/// identifying it by **drive ownership** (never by folder name — users
+/// can rename their home).
+///
+/// `id_fn` extracts a candidate `Uuid` from each item. The callsite
+/// commonly works with `FolderDto` (whose `id` is a `String`); the
+/// closure is `|f| Uuid::parse_str(&f.id).ok()`. Items whose ids can't
+/// be parsed are simply skipped — `position` ignores them.
+///
+/// Defined as a free function (not a trait method) so the
+/// `DriveRepository` trait stays `dyn`-compatible. Generic over both
+/// the repo (`R`) and the item shape (`T`); accepts both concrete repo
+/// types and `&dyn DriveRepository`.
+///
+/// Returns `None` when:
+///   * The user has no default drive (external users, pre-hook accounts).
+///   * The user's home root folder id isn't present in `items`.
+///   * The repo lookup errored (storage error is swallowed to None —
+///     callers wanting fail-loud semantics should call
+///     `home_root_folder_id_for` directly).
+pub async fn position_of_user_home_root_folder<R, T>(
+    drive_repo: &R,
+    user_id: Uuid,
+    items: &[T],
+    id_fn: impl Fn(&T) -> Option<Uuid>,
+) -> Option<usize>
+where
+    R: DriveRepository + ?Sized,
+{
+    let home_id = drive_repo
+        .home_root_folder_id_for(user_id)
+        .await
+        .ok()
+        .flatten()?;
+    items.iter().position(|item| id_fn(item) == Some(home_id))
+}

src/domain/repositories/folder_repository.rs

@@ -136,18 +136,6 @@ pub trait FolderRepository: Send + Sync + 'static {
     /// Permanently deletes a folder (used by the trash)
     async fn delete_folder_permanently(&self, folder_id: &str) -> Result<(), DomainError>;
 
-    /// Creates a root-level home folder for a user inside their personal drive.
-    /// Called during user registration / first login to maintain the wrapper-
-    /// folder convention through the D0 dual-write window (the wrapper itself
-    /// retires in a follow-up migration; for now it stays as a real folder
-    /// row stamped with `drive_id`).
-    async fn create_home_folder(
-        &self,
-        user_id: Uuid,
-        drive_id: Uuid,
-        name: String,
-    ) -> Result<Folder, DomainError>;
-
     /// Lists every folder in a subtree rooted at `folder_id` (inclusive).
     ///
     /// Uses ltree `<@` for a single GiST-indexed scan.  The result is