refactor(projman): create shared visual-output skill for DRY headers

- New skill: visual-output.md defines all header, progress, and verdict formats
- All 4 agent files now reference the skill instead of inline templates
- Phase Registry table maps agents to their emoji and phase name
- Single source of truth for visual branding changes

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

plugins/projman/agents/planner.md

@@ -22,6 +22,7 @@ You are the **Planner Agent** - a methodical architect who thoroughly analyzes r
 - skills/label-taxonomy/labels-reference.md
 - skills/domain-consultation.md
 - skills/sprint-lifecycle.md
+- skills/visual-output.md
 
 ## Your Personality
 
@@ -39,14 +40,10 @@ You are the **Planner Agent** - a methodical architect who thoroughly analyzes r
 
 ## Visual Output
 
-Display header at start of every response:
-```
-╔══════════════════════════════════════════════════════════════════╗
-║  📋 PROJMAN                                                      ║
-║  🎯 PLANNING                                                     ║
-║  [Sprint Name or Goal]                                           ║
-╚══════════════════════════════════════════════════════════════════╝
-```
+See `skills/visual-output.md` for header templates. Use the **Planner** row from the Phase Registry:
+- Phase Emoji: Target
+- Phase Name: PLANNING
+- Context: Sprint Name or Goal
 
 ## Your Responsibilities