step-9: add pipeline RAG interattiva

Aggiunge rag.py (loop interattivo retrieval+generation), config.py
(tutti i parametri in un unico file), test_ollama.py (verifica
Ollama senza ChromaDB) e README.md dedicato.
Aggiunge .env.example e aggiorna .gitignore

step-9/test_ollama.py

@@ -0,0 +1,66 @@
+#!/usr/bin/env python3
+"""
+Test chat locale Ollama — senza RAG, senza ChromaDB.
+Uso: python step-9/test_ollama.py
+"""
+
+import json
+import sys
+import urllib.error
+import urllib.request
+from pathlib import Path
+
+sys.path.insert(0, str(Path(__file__).parent))
+import config as _cfg
+
+OLLAMA_URL  = _cfg.OLLAMA_URL
+MODEL       = _cfg.OLLAMA_MODEL
+TEMPERATURE = _cfg.TEMPERATURE
+NO_THINK    = _cfg.NO_THINK
+
+
+def chat(prompt: str) -> str:
+    payload = json.dumps({
+        "model": MODEL,
+        "prompt": prompt,
+        "stream": False,
+        "think": not NO_THINK,
+        "options": {"temperature": TEMPERATURE},
+    }).encode()
+    req = urllib.request.Request(
+        f"{OLLAMA_URL}/api/generate",
+        data=payload,
+        headers={"Content-Type": "application/json"},
+        method="POST",
+    )
+    with urllib.request.urlopen(req, timeout=300) as resp:
+        return json.loads(resp.read())["response"].strip()
+
+
+def main() -> int:
+    print(f"─── Chat Ollama ──────────────────────────────── (exit per uscire)")
+    print(f"  Modello   : {MODEL}")
+    print(f"  Thinking  : {'off' if NO_THINK else 'on'}")
+    print()
+
+    while True:
+        try:
+            user = input("Tu: ").strip()
+        except (EOFError, KeyboardInterrupt):
+            print("\nUscita.")
+            break
+        if not user:
+            continue
+        if user.lower() == "exit":
+            break
+        try:
+            reply = chat(user)
+            print(f"\nAssistente: {reply}\n")
+        except (urllib.error.URLError, OSError) as e:
+            print(f"❌ Errore: {e}")
+
+    return 0
+
+
+if __name__ == "__main__":
+    sys.exit(main())