feat: project_id obbligatorio (gateway v2.4.0 + estensione v1.4.0)

- gateway: MemoryIn.project_id required (min_length=1) → POST senza project_id = 422
- estensione: qmem_store project_id Type.String (non più Optional), descrizione con obbligo e rinvio a qmem_meta; qmem_correct resta opzionale (eredita dal superseduto)
- README/playbook sez. 11.5 aggiornati

gateway/main.py

@@ -50,7 +50,7 @@ MAX_TEXT_LEN = int(os.environ.get("MAX_TEXT_LEN", "8000"))
 logging.basicConfig(level=logging.INFO, format="%(asctime)s %(levelname)s %(message)s")
 log = logging.getLogger("memory-gateway")
 
-app = FastAPI(title="Memory Gateway", version="2.3.0")
+app = FastAPI(title="Memory Gateway", version="2.4.0")
 qdrant = QdrantClient(url=QDRANT_URL, api_key=QDRANT_API_KEY)
 
 # Rate limit in-memory: {key: [timestamps]}
@@ -72,7 +72,7 @@ class MemoryIn(BaseModel):
     text: str = Field(min_length=1, max_length=MAX_TEXT_LEN)
     kind: Literal["decision", "fact", "episode", "preference"] = "fact"
     agent_id: Optional[str] = Field(default=None, max_length=64, description="Solo provenienza, nessun isolamento")
-    project_id: Optional[str] = Field(default=None, max_length=64)
+    project_id: str = Field(min_length=1, max_length=64, description="OBBLIGATORIO: progetto/dominio di appartenenza (kebab-case)")
     scope: Literal["agent", "project", "org"] = "agent"
     source: Optional[str] = Field(default=None, max_length=256)
     expires_at: Optional[str] = None  # ISO 8601