feat(ui): profile picker + per-profile vocabulary; transcribe invokes carry profileId; drop buildInitialPrompt

src/routes/+layout.svelte

@@ -17,6 +17,7 @@
     applyExternalPreferences,
     PREFERENCES_CHANGED_EVENT,
   } from "$lib/stores/preferences.svelte.js";
+  import { profilesStore } from "$lib/stores/profiles.svelte.ts";
   import { getCurrentWindow } from "@tauri-apps/api/window";
   import { listen } from "@tauri-apps/api/event";
   import { toasts } from "$lib/stores/toasts.svelte.js";
@@ -249,6 +250,9 @@
     // Detect and initialise the correct hotkey backend
     await initHotkeyBackend();
 
+    // Load profiles (per-profile vocabulary + initial prompt). Task 15.
+    await profilesStore.load();
+
     try {
       const whisper = await invoke("list_models");
       const parakeet = await invoke("list_parakeet_models");