fix(kon): float window sidebar, transcription doubling guard, branding

Float window fixes:
- Root layout now detects /float and /viewer URLs and hides Sidebar,
  Titlebar, TaskSidebar for secondary windows. Belt-and-braces fix
  since +layout@.svelte should handle this but may not in SPA mode.
- Float window title: "Ramble - To-do" → "Kon - To-do"

Transcription doubling guard:
- Added chunk_id deduplication set in DictationPage — if a chunk_id
  has already been processed, skip the duplicate result
- Set cleared on each new recording session

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

src/routes/+layout.svelte

@@ -7,8 +7,17 @@
   import Titlebar from "$lib/components/Titlebar.svelte";
   import { page, settings } from "$lib/stores/page.svelte.js";
 
+  import { page as sveltePage } from "$app/stores";
+
   let { children } = $props();
 
+  // Detect secondary windows (float, viewer) — they use +layout@.svelte
+  // but as a fallback, hide chrome if the URL matches
+  let isSecondaryWindow = $derived(
+    $sveltePage.url.pathname.startsWith("/float") ||
+    $sveltePage.url.pathname.startsWith("/viewer")
+  );
+
   // Recording indicator dot (follows mouse)
   let mouseX = $state(0);
   let mouseY = $state(0);
@@ -98,17 +107,22 @@
   ></div>
 {/if}
 
-<div class="flex flex-col h-screen w-screen overflow-hidden grain">
-  <Titlebar />
-  <div class="flex flex-1 min-h-0">
-    {#if page.current !== "first-run"}
-      <Sidebar />
-    {/if}
-    <div class="flex-1 overflow-hidden bg-bg">
-      {@render children()}
+{#if isSecondaryWindow}
+  <!-- Secondary windows (float, viewer) render children only — no shell chrome -->
+  {@render children()}
+{:else}
+  <div class="flex flex-col h-screen w-screen overflow-hidden grain">
+    <Titlebar />
+    <div class="flex flex-1 min-h-0">
+      {#if page.current !== "first-run"}
+        <Sidebar />
+      {/if}
+      <div class="flex-1 overflow-hidden bg-bg">
+        {@render children()}
+      </div>
+      {#if page.taskSidebarOpen && page.current !== "first-run"}
+        <TaskSidebar />
+      {/if}
     </div>
-    {#if page.taskSidebarOpen && page.current !== "first-run"}
-      <TaskSidebar />
-    {/if}
   </div>
-</div>
+{/if}