fix(harness): workspace + write-URL + L2 tests per accesso REST reale

Bug trovato provando la connessione reale col .env: il write endpoint vive su un
PATH DEDICATO /vector/write/v1/ (non /vector/v1/), e il modello Config ha write_rest/
vector_write_rest a TOP-LEVEL (non nidificati in vector_db).

- .env.example: aggiunge THOTH_VEC_WRITE_REST_URL (path dedicato del writer, con
  avviso che le due chiavi valgono su path separati).
- workspaces/chirone-test.yaml: riscritto allineato a chirone.example.yaml + config.py
  (vector_rest/vector_write_rest top-level; write_rest punta a THOTH_VEC_WRITE_REST_URL).
- tests/l2/*: corretti gli accessi strutturali (ws.vector_write_rest invece di
  ws.vector_db.write_rest; ws.vector_rest invece di ws.vector_db.rest).
  test_value_grounding_real skip-when-import-fails su nsp.lshindex (modulo deferred da B3).

Verificato end-to-end: save_one_memory (embeddings -> writer REST /vector/write/v1/
-> upsert pgvector -> read-back reader) PASSED. Suite L0+L1: 109 passed. Suite L2:
4 passed, 1 skipped (lshindex deferred).

Nota operativa: THOTH_SSL_CA va lasciato VUOTO sulla workstation (cert GoDaddy
pubblico in certifi). I campi direct-transport (THOTH_DB_*, THOTH_VEC_PASSWORD)
sono obbligatori per il modello ma inutilizzati in transport=rest: riempiti con
dummy nel .env locale (come faceva ChironeWp3).

harness/workspaces/chirone-test.yaml

@@ -1,31 +1,20 @@
-# Workspace ThothII -- Chirone (DWH remoto) per i test L2.
-# I segreti vivono SOLO in .env (${THOTH_*}). Endpoint + ruolo dai parametri di
-# connessione L2 (spec Testing Strategy): DWH read-only via PostgREST, pgvector
-# con doppia key (reader/writer) sullo stesso endpoint, TLS self-signed (CA = leaf).
-
-name: chirone-test
-description: "Chirone DWH -- L2 test workspace"
+# Workspace ThothII — Chirone (DWH remoto) per i test L2.
+# Struttura allineata a workspaces/chirone.example.yaml e nsp/config.py.
+# I segreti vivono SOLO in .env (${THOTH_*}).
 
 database:
-  database: postgres
+  host: ${THOTH_DB_HOST}
+  port: ${THOTH_DB_PORT}
+  database: ${THOTH_DB_NAME}
   schema: datawarehouse
+  user: ${THOTH_DB_USER}
+  password: ${THOTH_DB_PASSWORD}
   transport: rest
-  rest:
-    base_url: ${THOTH_DWH_REST_URL}
-    api_key: ${THOTH_DWH_API_KEY}
-    ssl_ca: ${THOTH_SSL_CA}
 
-vector_db:
-  collection: chirone_docs
-  dim: 768
-  rest:
-    base_url: ${THOTH_VEC_REST_URL}
-    api_key: ${THOTH_VEC_API_KEY}
-    ssl_ca: ${THOTH_SSL_CA}
-  write_rest:
-    base_url: ${THOTH_VEC_REST_URL}
-    api_key: ${THOTH_VEC_WRITE_API_KEY}
-    ssl_ca: ${THOTH_SSL_CA}
+rest:
+  base_url: ${THOTH_DWH_REST_URL}
+  api_key: ${THOTH_DWH_API_KEY}
+  ssl_ca: ${THOTH_SSL_CA}
 
 paths:
   artifacts: artifacts
@@ -33,12 +22,43 @@ paths:
   sessions: sessions
 
 embeddings:
-  provider: ollama
   base_url: ${THOTH_OLLAMA_URL}
   model: nomic-embed-text-v2-moe
   dim: 768
   batch_size: 64
 
+# LOADING diretto del pgvector (server-only). Su workstation la lettura passa da
+# vector_rest; i campi direct-transport non sono usati ma il modello DatabaseConfig
+# li richiede, per cui si appoggiano alle stesse variabili del server (popolate nel
+# .env del server; sul workstation restano dummy/inediti finche' transport=rest).
+vector_db:
+  host: ${THOTH_VEC_HOST}
+  port: ${THOTH_VEC_PORT}
+  database: postgres
+  schema: vectors
+  user: ${THOTH_VEC_USER}
+  password: ${THOTH_VEC_PASSWORD}
+
+# LETTURA del pgvector via REST remota (rpc search_similar), ruolo vector_reader.
+vector_rest:
+  base_url: ${THOTH_VEC_REST_URL}
+  api_key: ${THOTH_VEC_API_KEY}
+  ssl_ca: ${THOTH_SSL_CA}
+
+# SCRITTURA controllata del pgvector via REST remota (upsert/hash via RPC allowlist),
+# ruolo vector_writer. Path DEDICATO /vector/write/v1/ (diverso dal reader): la chiave
+# writer vale solo qui, la reader solo su /vector/v1/. Key SEPARATA dalla lettura.
+vector_write_rest:
+  base_url: ${THOTH_VEC_WRITE_REST_URL}
+  api_key: ${THOTH_VEC_WRITE_API_KEY}
+  ssl_ca: ${THOTH_SSL_CA}
+
+vector:
+  max_chunk_chars: 4000
+
+search:
+  rrf_k: 60
+
 execution:
   allow: [cte_test, explain, preview, aggregate, export]
   max_preview_rows: 10