feat(drive): add drive picker in sidebar

- select by default the home drive

frontend/src/lib/stores/drives.svelte.ts

@@ -0,0 +1,62 @@
+/**
+ * Drives store — caches `GET /api/drives` so the picker, the breadcrumb
+ * icon, and the session bootstrap all share one fetch. Idempotent `load()`.
+ *
+ * Identifying the user's home: always via `default_for_user`, never by
+ * folder name (users can rename "Personal").
+ */
+import { listDrives } from '$lib/api/endpoints/drives';
+import type { Drive } from '$lib/api/types';
+
+class DrivesStore {
+	drives = $state<Drive[]>([]);
+	loaded = $state(false);
+	private inflight: Promise<Drive[]> | null = null;
+
+	async load(): Promise<Drive[]> {
+		if (this.loaded) return this.drives;
+		if (this.inflight) return this.inflight;
+		this.inflight = (async () => {
+			try {
+				this.drives = await listDrives();
+			} catch {
+				this.drives = [];
+			} finally {
+				this.loaded = true;
+				this.inflight = null;
+			}
+			return this.drives;
+		})();
+		return this.inflight;
+	}
+
+	/** Force a refresh after a mutation (rename, member change, …). */
+	invalidate(): void {
+		this.loaded = false;
+		this.drives = [];
+	}
+
+	/** Caller's default-personal drive (one per internal user), or null. */
+	findDefault(): Drive | null {
+		return this.drives.find((d) => d.default_for_user != null) ?? null;
+	}
+
+	/** Drive whose root folder UUID matches `id`, or null. */
+	findByRootFolderId(id: string | null | undefined): Drive | null {
+		if (!id) return null;
+		return this.drives.find((d) => d.root_folder_id === id) ?? null;
+	}
+}
+
+export const drives = new DrivesStore();
+
+/**
+ * Picker / breadcrumb icon for a drive:
+ *   home   — default-personal (the user's home)
+ *   folder — secondary personal drive
+ *   users  — shared / team drive
+ */
+export function driveIcon(d: Drive): string {
+	if (d.default_for_user) return 'home';
+	return d.kind === 'shared' ? 'users' : 'folder';
+}

frontend/src/lib/stores/session.svelte.ts

@@ -7,7 +7,7 @@
  * folder and land on the shared-with-me view.
  */
 import { fetchMe, tryRefresh } from '$lib/api/endpoints/auth';
-import { listRootFolders } from '$lib/api/endpoints/folders';
+import { drives } from '$lib/stores/drives.svelte';
 import type { User } from '$lib/api/types';
 
 class SessionStore {
@@ -41,20 +41,21 @@ class SessionStore {
 	}
 
 	/**
-	 * Resolve the home folder (first entry of GET /api/folders). Externals
-	 * (grant-only) have no home folder, so this is skipped for them.
+	 * Resolve the caller's default personal drive's root folder — the landing
+	 * point for `/files` and the `/` redirect. Externals (grant-only) have no
+	 * personal drive, so this is skipped for them.
+	 *
+	 * Identifies the default via `default_for_user`, not folder name: users
+	 * can rename "Personal" without breaking this lookup.
 	 */
 	async loadHomeFolder(): Promise<string | null> {
 		if (this.homeFolderId) return this.homeFolderId;
 		if (this.isExternalUser) return null;
-		try {
-			const folders = await listRootFolders();
-			if (folders.length > 0) {
-				this.homeFolderId = folders[0].id;
-				this.homeFolderName = folders[0].name;
-			}
-		} catch {
-			/* leave null — caller handles */
+		await drives.load();
+		const def = drives.findDefault();
+		if (def) {
+			this.homeFolderId = def.root_folder_id;
+			this.homeFolderName = def.name;
 		}
 		return this.homeFolderId;
 	}