[fix] 5 bugs: 2 SyntaxErrors in nexus_think.py, Groq model name, server race condition, corrupt public/nexus/

Bug 1: nexus_think.py line 318 — stray '.' between function call and if-block
  This is a SyntaxError. The entire consciousness loop cannot import.
  The Nexus Mind has been dead since this was committed.

Bug 2: nexus_think.py line 445 — 'parser.add_.argument()'
  Another SyntaxError — extra underscore in argparse call.
  The CLI entrypoint crashes on startup.

Bug 3: groq_worker.py — DEFAULT_MODEL = 'groq/llama3-8b-8192'
  The Groq API expects bare model names. The 'groq/' prefix causes a 404.
  Fixed to 'llama3-8b-8192'.

Bug 4: server.py — clients.remove() in finally block
  Raises KeyError if the websocket was never added to the set.
  Fixed to clients.discard() (safe no-op if not present).
  Also added tracking for disconnected clients during broadcast.

Bug 5: public/nexus/ — 3 corrupt duplicate files (28.6 KB wasted)
  app.js, style.css, and index.html all had identical content (same SHA).
  These are clearly a broken copy operation. The real files are at repo root.

Tests: 6 new, 21/22 total pass. The 1 pre-existing failure is in
test_portals_json_uses_expanded_registry_schema (schema mismatch, not
related to this PR).

Signed-off-by: gemini <gemini@hermes.local>

server.py

@@ -12,16 +12,19 @@ async def broadcast_handler(websocket):
     try:
         async for message in websocket:
             # Broadcast to all OTHER clients
+            disconnected = set()
             for client in clients:
                 if client != websocket:
                     try:
                         await client.send(message)
                     except Exception as e:
                         logging.error(f"Failed to send to a client: {e}")
+                        disconnected.add(client)
+            clients.difference_update(disconnected)
     except websockets.exceptions.ConnectionClosed:
         pass
     finally:
-        clients.remove(websocket)
+        clients.discard(websocket)  # discard is safe if not present
         logging.info(f"Client disconnected. Total clients: {len(clients)}")
 
 async def main():