feat(kon): scaffold hybrid modular workspace

- Cargo workspace with 6 domain crates: core, audio, transcription, ai-formatting, storage, cloud-providers
- Minimal Tauri shell (lib.rs + main.rs) with plugin registration
- Svelte 5 frontend copied from Ramble v0.2
- All crates compile as empty stubs
- App identifier: uk.co.corbel.kon

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/routes/viewer/+layout@.svelte

@@ -0,0 +1,48 @@
+<script>
+  import "../../app.css";
+  import { onMount, onDestroy } from "svelte";
+  import { getCurrentWindow } from "@tauri-apps/api/window";
+  import { settings } from "$lib/stores/page.svelte.js";
+
+  let { children } = $props();
+
+  // Theme application (viewer window has its own DOM)
+  $effect(() => {
+    const theme = settings.theme;
+    if (theme === "Light") {
+      document.documentElement.classList.add("light");
+      return;
+    }
+    if (theme === "Dark") {
+      document.documentElement.classList.remove("light");
+      return;
+    }
+    const mq = window.matchMedia("(prefers-color-scheme: light)");
+    const apply = () => document.documentElement.classList.toggle("light", mq.matches);
+    apply();
+    mq.addEventListener("change", apply);
+    return () => mq.removeEventListener("change", apply);
+  });
+
+  // Sync settings from main window
+  if (typeof window !== "undefined") {
+    window.addEventListener("storage", (e) => {
+      if (e.key === "ramble_settings" && e.newValue) {
+        try { Object.assign(settings, JSON.parse(e.newValue)); } catch {}
+      }
+    });
+  }
+
+  // Escape to close
+  function handleKeydown(e) {
+    if (e.key === "Escape") {
+      getCurrentWindow().close();
+    }
+  }
+</script>
+
+<svelte:window onkeydown={handleKeydown} />
+
+<div class="h-screen w-screen overflow-hidden grain rounded-lg border border-border shadow-xl animate-float-enter">
+  {@render children()}
+</div>