soul: parameterize CGI ID + add dharma_room_turn handler

- soul.el: SOUL_CGI_ID, SOUL_ENGRAM_PATH, SOUL_IDENTITY env vars;
  state_set("soul_snapshot_path") so callers can find it; only call
  init_soul_edges() when cgi_id == "ntn-genesis"
- chat.el: handle_dharma_room_turn — soul builds its own context from its
  own engram, assembles system prompt, calls LLM, persists episodic memory;
  also fix is_new_tool scoping bug in handle_chat_agentic (use has_tool)
- routes.el: wire dharma_room_turn event type before chat_as_soul branch
- rebuild dist/neuron: handle_dharma_room_turn now compiled in

dist/studio.c

@@ -35,6 +35,7 @@ el_val_t agentic_tools_literal(void);
 el_val_t dispatch_tool(el_val_t tool_name, el_val_t tool_input);
 el_val_t handle_chat_agentic(el_val_t body);
 el_val_t handle_chat_as_soul(el_val_t body);
+el_val_t handle_dharma_room_turn(el_val_t body);
 el_val_t auto_persist(el_val_t req, el_val_t resp);
 el_val_t auth_headers(el_val_t tok);
 el_val_t axon_get(el_val_t path);