Centralize role emojis: Witness 👁→🦉, Deacon 🦉→🐺

Added centralized emoji constants in internal/constants/constants.go
for easy customization. Updated all files that hardcoded role emojis
to use the new constants.

Changes:
- Witness emoji: 👁 (eye) → 🦉 (owl) - less creepy, matches visual identity
- Deacon emoji: 🦉 (owl) → 🐺 (wolf) - matches hierarchy prompt (wolf in engine room)
- Added RoleEmoji() helper function for string-based lookups
- Maintained backwards compatibility with legacy role names

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

internal/cmd/feed.go

@@ -70,7 +70,7 @@ Event symbols:
   ✓  completed         - Issue closed or step completed
   ✗  failed            - Step or issue failed
   ⊘  deleted           - Issue removed
-  👁  patrol_started   - Witness began patrol cycle
+  🦉  patrol_started   - Witness began patrol cycle
   ⚡  polecat_nudged   - Worker was nudged
   🎯  sling            - Work was slung to worker
   🤝  handoff          - Session handed off