Rename directories to plural form: skill/ → skills/, agent/ → agents/, command/ → commands/

- Rename skill/ to skills/ for consistency with naming conventions
- Rename agent/ to agents/ and command/ to commands/
- Update AGENTS.md with all directory references
- Update scripts/test-skill.sh paths
- Update prompts/athena.txt documentation

This aligns with best practices of using plural directory names and updates
all documentation to reflect the new structure.

commands/reflection.md

@@ -0,0 +1,20 @@
+---
+description: Toggle reflection mode on/off for automatic skill improvement detection
+---
+
+Reflection mode is now set to: $1
+
+When reflection mode is **ON**, I will:
+- Actively monitor for user correction signals during conversation
+- Detect patterns where you correct my behavior  
+- Automatically suggest skill improvements when clear signals detected
+- Proactively ask "Should I reflect on this?" when corrections occur
+
+When reflection mode is **OFF** (default), I will:
+- Only perform reflection when explicitly requested
+- Respond to explicit commands like "reflect on [skill]"
+- No automatic signal detection or suggestions
+
+Current mode: **$1**
+
+Note: This setting is session-scoped and will reset to OFF in new sessions.