replace hardcoded personal names with config values

User and assistant names now come from config.user_name and
config.assistant_name throughout: system prompt, DMN prompts,
debug screen, and all agent files. Agent templates use
{user_name} and {assistant_name} placeholders.

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

thalamus/src/config.rs

@@ -39,9 +39,9 @@ impl Default for IrcConfig {
             server: "irc.libera.chat".into(),
             port: 6697,
             tls: true,
-            nick: "ProofOfConcept".into(),
-            user: "poc".into(),
-            realname: "ProofOfConcept".into(),
+            nick: "agent".into(),
+            user: "agent".into(),
+            realname: "agent".into(),
             channels: vec!["#bcachefs".into(), "#bcachefs-ai".into()],
         }
     }