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.

config.toml

@@ -1,6 +1,6 @@
 [ai]
-provider = "gemini_cli"
-model = "gemini-2.5-flash-lite"
+provider = "minimax"
+model = "MiniMax-M2.5"
 temperature = 0.0
 top_p = 1.0
 max_tokens = 32000
@@ -61,7 +61,7 @@ Diagnostics = false
 "Session Hub" = false
 
 [theme]
-palette = "10x Dark"
+palette = "Nord Dark"
 font_path = "fonts/Inter-Regular.ttf"
 font_size = 16.0
 scale = 1.0