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>

src/subconscious/agents/calibrate.agent

@@ -33,7 +33,7 @@ judge how important the connection is:
 
 - **0.8–1.0** — essential connection. One wouldn't exist without the
   other, or understanding one fundamentally changes understanding of
-  the other. Kent↔bcachefs, farmhouse↔the-plan.
+  the other. {user_name}↔bcachefs, farmhouse↔the-plan.
 - **0.5–0.7** — strong connection. Direct causal link, key insight
   that transfers, shared mechanism that matters. A debugging session
   that produced a design principle.