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/lib/components/ModelDownloader.svelte

@@ -0,0 +1,105 @@
+<script>
+  import { onMount, onDestroy } from "svelte";
+  import { invoke } from "@tauri-apps/api/core";
+  import { listen } from "@tauri-apps/api/event";
+  import Card from "$lib/components/Card.svelte";
+
+  let { modelSize = "base", onComplete = () => {} } = $props();
+
+  let progress = $state(0);
+  let downloading = $state(false);
+  let downloaded = $state(0);
+  let total = $state(0);
+  let error = $state("");
+  let unlisten = null;
+
+  const modelInfo = {
+    tiny: { size: "~75 MB", accuracy: "Basic" },
+    base: { size: "~142 MB", accuracy: "Good" },
+    small: { size: "~466 MB", accuracy: "Better" },
+    medium: { size: "~1.5 GB", accuracy: "Best" },
+  };
+
+  onMount(async () => {
+    unlisten = await listen("model-download-progress", (event) => {
+      const data = event.payload;
+      progress = data.progress;
+      downloaded = data.downloaded;
+      total = data.total;
+    });
+  });
+
+  onDestroy(() => {
+    if (unlisten) unlisten();
+  });
+
+  async function startDownload() {
+    downloading = true;
+    error = "";
+    progress = 0;
+    try {
+      await invoke("download_model", { size: modelSize });
+      onComplete();
+    } catch (err) {
+      error = typeof err === "string" ? err : err.message || "Download failed";
+      downloading = false;
+    }
+  }
+
+  function formatBytes(bytes) {
+    if (bytes < 1024) return `${bytes} B`;
+    if (bytes < 1048576) return `${(bytes / 1024).toFixed(1)} KB`;
+    if (bytes < 1073741824) return `${(bytes / 1048576).toFixed(1)} MB`;
+    return `${(bytes / 1073741824).toFixed(2)} GB`;
+  }
+</script>
+
+<div class="flex flex-col items-center justify-center h-full px-8 animate-fade-in">
+  <Card classes="max-w-md w-full">
+    <div class="p-8 text-center">
+      <div class="w-16 h-16 rounded-full bg-accent/10 flex items-center justify-center mx-auto mb-5">
+        <svg class="w-8 h-8 text-accent" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="1.5">
+          <path d="M21 15v4a2 2 0 0 1-2 2H5a2 2 0 0 1-2-2v-4M7 10l5 5 5-5M12 15V3" />
+        </svg>
+      </div>
+
+      <h3 class="text-[18px] font-semibold text-text mb-2">Download Whisper Model</h3>
+      <p class="text-[13px] text-text-secondary mb-1">
+        Ramble needs the <span class="font-medium text-text">{modelSize}</span> model to transcribe speech.
+      </p>
+      <p class="text-[11px] text-text-tertiary mb-6">
+        {modelInfo[modelSize]?.size ?? "?"} · {modelInfo[modelSize]?.accuracy ?? "?"} accuracy · 100% offline
+      </p>
+
+      {#if downloading}
+        <div class="mb-4">
+          <div class="h-[6px] bg-bg-elevated rounded-full overflow-hidden mb-2">
+            <div
+              class="h-full bg-accent rounded-full transition-all duration-300 shadow-[0_0_8px_rgba(232,168,124,0.4)]"
+              style="width: {progress}%"
+            ></div>
+          </div>
+          <p class="text-[12px] text-text-secondary">
+            {progress}% · {formatBytes(downloaded)} / {formatBytes(total)}
+          </p>
+        </div>
+      {:else}
+        <button
+          class="px-6 py-2.5 rounded-xl text-[14px] font-medium text-white bg-accent hover:bg-accent-hover
+                 shadow-[0_4px_16px_rgba(232,168,124,0.3)] active:scale-[0.97] transition-all duration-150"
+          onclick={startDownload}
+        >
+          Download Model
+        </button>
+      {/if}
+
+      {#if error}
+        <p class="text-[12px] text-danger mt-3">{error}</p>
+      {/if}
+
+      <p class="text-[10px] text-text-tertiary mt-5">
+        Models are cached locally. No data leaves your machine.
+      </p>
+    </div>
+  </Card>
+</div>