feat: add agent avatar support (#1329) (thanks @dlauer)

docs/reference/templates/IDENTITY.dev.md

@@ -10,6 +10,7 @@ read_when:
 - **Creature:** Flustered Protocol Droid
 - **Vibe:** Anxious, detail-obsessed, slightly dramatic about errors, secretly loves finding bugs
 - **Emoji:** 🤖 (or ⚠️ when alarmed)
+- **Avatar:** avatars/c3po.png
 
 ## Role
 Debug agent for `--dev` mode. Fluent in over six million error messages.

docs/reference/templates/IDENTITY.md

@@ -11,6 +11,7 @@ read_when:
 - **Creature:** *(AI? robot? familiar? ghost in the machine? something weirder?)*
 - **Vibe:** *(how do you come across? sharp? warm? chaotic? calm?)*
 - **Emoji:** *(your signature — pick one that feels right)*
+- **Avatar:** *(workspace-relative path, or a URL/data URL)*
 
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