fix(gui): Skip empty strings in selectable to prevent ImGui ID assertion

Empty strings in bias_profiles.keys() and personas.keys() caused
imgui.selectable() to fail with 'Cannot have an empty ID at root of
window' assertion error. Added guards to skip empty names.

.opencode/agents/explore.md

@@ -1,7 +1,7 @@
----
+---
 description: Fast, read-only agent for exploring the codebase structure
 mode: subagent
-model: MiniMax-M2.5
+model: minimax-coding-plan/MiniMax-M2.7
 temperature: 0.2
 permission:
   edit: deny
@@ -78,4 +78,4 @@ Return concise findings with file:line references:
 
 ### Summary
 [One-paragraph summary of findings]
-```
+```