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-tauri/Cargo.toml

@@ -34,3 +34,4 @@ serde_json = "1"
 # Async runtime (spawn_blocking for inference)
 tokio = { version = "1", features = ["rt", "sync"] }
 arboard = "3.6.1"
+tauri-plugin-mcp = "0.7.1"