fix(launch): reliable Windows launcher; feat(ui): compact sidebar, Vite toggle, chat Think toggle

Ported from the private repo via bin/publish.sh, plus a manual catch-up
on files that had drifted out of sync before today:

- launch_nexus.ps1: health-check based restart decisions instead of a
  bare port-listen check (a wedged leftover process squatting a port
  used to look "already running" and block the real service from
  starting), a script-path quoting fix for Start-Process, hidden
  console via a wscript.exe wrapper (bin/launch_nexus_hidden.vbs), and
  a taskbar/window icon for the native app window.
- Sidebar: slim icon+text nav rows instead of bulky bordered buttons,
  tighter spacing throughout.
- Settings: full-width layout, a Vite dev-server Start/Stop toggle
  (synapse/frontend_manager.py + /frontend/* endpoints), and the
  Linux-only Icon Branding section now gated on the new /status
  `platform` field instead of always rendering.
- Chatbot: a Think toggle next to the model picker, so extended
  thinking can be flipped without leaving the chat page.
- management/ncp.py: faster start/stop polling (0.25s steps instead of
  1s), Vite no longer blocks `ncp start` on Linux and is skipped
  outright on Windows.

Note: the private repo also has a Mail (IMAP/SMTP) feature; it's
intentionally not included here, so the Mail-only pieces of main.py,
App.jsx, and requirements-windows.txt were left out of this port.

install-windows.ps1

@@ -217,12 +217,16 @@ if ($Shadowed) {
 # -- Desktop shortcut ----------------------------------------------------------
 Write-Step "Creating desktop shortcut"
 try {
-    $Launcher = Join-Path $RepoRoot "launch_nexus.ps1"
+    # Target the .vbs wrapper, not powershell.exe directly: on Windows 11 with
+    # Windows Terminal as the default terminal app, -WindowStyle Hidden on a
+    # console-subsystem process is often ignored and a terminal tab flashes up
+    # anyway. wscript.exe never allocates a console at all, sidestepping that.
+    $Launcher = Join-Path $RepoRoot "bin\launch_nexus_hidden.vbs"
     $LnkPath = Join-Path ([Environment]::GetFolderPath("Desktop")) "NexusOS.lnk"
     $ws = New-Object -ComObject WScript.Shell
     $lnk = $ws.CreateShortcut($LnkPath)
-    $lnk.TargetPath = "powershell.exe"
-    $lnk.Arguments = "-NoProfile -ExecutionPolicy Bypass -WindowStyle Hidden -File `"$Launcher`""
+    $lnk.TargetPath = "$env:WINDIR\System32\wscript.exe"
+    $lnk.Arguments = "`"$Launcher`""
     $lnk.WorkingDirectory = $RepoRoot
     $lnk.Description = "Launch NexusOS"
     $Ico = Join-Path $RepoRoot "assets\NexusOS.ico"