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.

synapse/main.py

@@ -10,6 +10,7 @@ from uuid import UUID
 
 import httpx
 import os as _os
+import platform as _platform
 from pathlib import Path
 from fastapi import FastAPI, HTTPException, Body
 from fastapi.middleware.cors import CORSMiddleware
@@ -19,6 +20,7 @@ from .nexus_config import settings, VERSION, DEFAULT_CHAT_MODEL
 from .chat import generate_chat_response, stream_chat_response, _synapse_trace
 from . import chat as _chat
 from .ollama_manager import initialize_ollama, initialize_ollama_async, get_ollama_manager
+from . import frontend_manager as _frontend_manager
 from .playbook_manager import PlaybookManager
 from . import tools as _tools
 
@@ -226,7 +228,7 @@ async def root():
                   if (ollama is not None and hasattr(ollama, "get_status")) else None)
     except Exception:
         status = None
-    return {"status": "online", "version": VERSION, "ollama": status}
+    return {"status": "online", "version": VERSION, "ollama": status, "platform": _platform.system().lower()}
 
 
 # -------------------------
@@ -788,6 +790,31 @@ async def ollama_stop_endpoint():
     except Exception as e:
         raise HTTPException(status_code=500, detail=str(e))
 
+# -------------------------
+# Vite Dev Server (Settings toggle) - dev-only convenience, not part of the
+# single-process production path. Runs via a thread so npm's own startup time
+# doesn't block the event loop, matching the Ollama start/stop pattern above.
+# -------------------------
+@app.get("/frontend/status")
+async def frontend_status_endpoint():
+    return {"running": await _asyncio.to_thread(_frontend_manager.is_running)}
+
+
+@app.post("/frontend/start")
+async def frontend_start_endpoint():
+    try:
+        return await _asyncio.to_thread(_frontend_manager.start)
+    except Exception as e:
+        raise HTTPException(status_code=500, detail=str(e))
+
+
+@app.post("/frontend/stop")
+async def frontend_stop_endpoint():
+    try:
+        return await _asyncio.to_thread(_frontend_manager.stop)
+    except Exception as e:
+        raise HTTPException(status_code=500, detail=str(e))
+
 # -------------------------
 # Playbooks List (existing)
 # -------------------------