Drop redundant system prompt — all info is in memory nodes

The system prompt duplicated what's already in core-personality and
other memory nodes. Moving everything to memory means it's all
trainable data rather than hardcoded strings.

Co-Authored-By: Proof of Concept <poc@bcachefs.org>

src/mind/unconscious.rs

@@ -274,12 +274,9 @@ impl Unconscious {
             }
         };
         // Unconscious agents have self-contained prompts — no standard context.
-        let system_prompt = String::new();
-        let personality = Vec::new();
-
         let client = crate::agent::api::ApiClient::new(base_url, api_key, model);
         let agent = crate::agent::Agent::new(
-            client, system_prompt, personality,
+            client, Vec::new(),
             app, String::new(), None,
             crate::agent::tools::ActiveTools::new(),
             auto.tools.clone(),