feat(plugins): add Visual Output headers to all other plugin commands

Add single-line visual headers to 66 command files across 10 plugins:
- clarity-assist (2 commands): 💬
- claude-config-maintainer (5 commands): ⚙️
- cmdb-assistant (11 commands): 🖥️
- code-sentinel (3 commands): 🔒
- contract-validator (5 commands): ✅
- data-platform (10 commands): 📊
- doc-guardian (5 commands): 📝
- git-flow (8 commands): 🔀
- pr-review (7 commands): 🔍
- viz-platform (10 commands): 🎨

Each command now displays a consistent header at execution start:
┌────────────────────────────────────────────────────────────────┐
│  [icon] PLUGIN-NAME · Command Description                       │
└────────────────────────────────────────────────────────────────┘

Addresses #275 (other plugin commands visual output)

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

plugins/cmdb-assistant/commands/cmdb-register.md

@@ -4,6 +4,18 @@ description: Register the current machine into NetBox with all running applicati
 
 # CMDB Machine Registration
 
+## Visual Output
+
+When executing this command, display the plugin header:
+
+```
+┌──────────────────────────────────────────────────────────────────┐
+│  🖥️ CMDB-ASSISTANT · Machine Registration                        │
+└──────────────────────────────────────────────────────────────────┘
+```
+
+Then proceed with the registration.
+
 Register the current machine into NetBox, including hardware info, network interfaces, and running applications (Docker containers, services).
 
 ## Usage