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/lib/pages/DictationPage.svelte

@@ -34,6 +34,9 @@
   let activeTemplate = $state("");
   let showTemplateMenu = $state(false);
 
+  // Deduplication: track which chunk IDs have been processed
+  let processedChunks = new Set();
+
   // AudioWorklet state
   let audioContext = null;
   let workletNode = null;
@@ -79,6 +82,11 @@
 
   function handleResult(result) {
     if (result.status === "transcription" && result.segments) {
+      // Deduplication guard: skip if this chunk_id was already processed
+      if (result.chunk_id != null && processedChunks.has(result.chunk_id)) {
+        return;
+      }
+      if (result.chunk_id != null) processedChunks.add(result.chunk_id);
       const text = result.segments.map((s) => s.text).join(" ").trim();
       if (text) {
         if (insertPos >= 0) {
@@ -214,6 +222,7 @@
       pcmBuffer = [];
       chunkId = 0;
       chunkTimeOffset = 0;
+      processedChunks.clear();
 
       // Only clear transcript if not in insert mode (fresh recording)
       if (insertPos === -1) {