Port Windows installer/ncp fixes and a real nomic-embed-text default

- install-windows.ps1: warn about a leftover profile-based ncp() that
  would shadow ncp.cmd; the "press any key to close" footer now skips
  the wait when stdin is redirected (was hanging indefinitely) and
  exits cleanly instead of Stop-Process when it owns the window; pulls
  nomic-embed-text alongside the chat/memory models.
- management/ncp.py: ncp start / start -b bring Ollama up automatically;
  longer timeout + real error message on a slow model warm.
- synapse/nexus_config.py: DEFAULT_EMBED_MODEL, single source of truth
  alongside DEFAULT_CHAT_MODEL/DEFAULT_MEMORY_MODEL.
- synapse/ollama_manager.py: is_available() cached instead of spawning a
  process per /status poll; is_running() timeout dropped 2s -> 0.5s so a
  healthy backend stops reading as dead; embed() reads the new default
  instead of a hardcoded string; de-duplicated serve-env setup.

Ported via bin/publish.sh from NexusOS-jon.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

management/ncp.py

@@ -304,14 +304,19 @@ def stop_service(svc: Service) -> bool:
 def start_ollama() -> None:
     """Driven through the backend endpoint (the path the control panel uses)
     rather than launching the binary, because OllamaManager owns model and GPU
-    selection. Requires the backend to be up."""
+    selection. Requires the backend to be up.
+
+    Long timeout: the endpoint blocks until the model is warmed - weights read
+    off disk into RAM/VRAM - which the web UI's own "Loading model..." button
+    state calls out as routinely taking about a minute, not just the Ollama
+    process launching."""
     print("Starting OLLAMA...")
     req = urllib.request.Request("http://localhost:8000/ollama/start", method="POST")
     try:
-        urllib.request.urlopen(req, timeout=30).read(1)
+        urllib.request.urlopen(req, timeout=180).read(1)
         print("NEXUS OLLAMA STARTED")
-    except Exception:
-        print("  OLLAMA start request failed (backend not reachable on :8000)")
+    except Exception as e:
+        print(f"  OLLAMA start failed: {e}")
 
 
 def stop_ollama() -> None:
@@ -339,6 +344,7 @@ def cmd_start(target) -> None:
         launch(SERVICES["memory"]); wait_for_port(SERVICES["memory"])
     elif target in ("--backend", "-b"):
         launch(SERVICES["backend"]); wait_for_port(SERVICES["backend"])
+        start_ollama()
     elif target in ("--frontend", "-f"):
         launch(SERVICES["frontend"]); wait_for_port(SERVICES["frontend"])
     elif target in ("--ai", "-a"):
@@ -349,6 +355,7 @@ def cmd_start(target) -> None:
         launch(SERVICES["backend"])
         wait_for_port(SERVICES["memory"])
         wait_for_port(SERVICES["backend"])
+        start_ollama()
         launch(SERVICES["frontend"])
         wait_for_port(SERVICES["frontend"])
     else:
@@ -656,7 +663,7 @@ Commands:
    --memory,  -m        Start only the memory service
    --frontend,-f        Start only the frontend
    --backend, -b        Start only the backend
-   --ai,      -a        Start the AI (Ollama) — manual; not started by default
+   --ai,      -a        Start only the AI (Ollama); `start`/`start -b` already include it
 
   stop                  Stop ALL Nexus services
    --memory,  -m        Stop only the memory service