fix: artifact-ai output duplication and provider update

- Add explicit output template {result} to prevent input being appended
- Switch provider from claude to opencode-deepseek for better PlantUML generation
- Fix plantuml cleanup to extract only first diagram when AI outputs duplicates
- Add mermaid cleanup to handle duplicate diagrams
- Set result variable instead of using print() for proper output capture

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

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

smarttools/artifact-ai/config.yaml

@@ -16,6 +16,8 @@ arguments:
     required: true
     description: Natural language instruction for generating or modifying the artifact
 
+output: "{result}"
+
 steps:
   # Step 1: Build format-specific prompt and call AI
   - type: code
@@ -120,7 +122,7 @@ steps:
 
   - type: prompt
     prompt: "{prompt}"
-    provider: claude
+    provider: opencode-deepseek
     output_var: ai_output
 
   # Step 2: Clean up output based on format
@@ -156,10 +158,23 @@ steps:
               code = json_match.group(0)
 
       elif format == 'plantuml':
-          # Ensure proper tags
-          if not code.strip().startswith('@start'):
-              code = '@startuml\n' + code
-          if not code.strip().endswith('@enduml') and '@enduml' not in code:
-              code = code + '\n@enduml'
+          # Extract first complete @startuml...@enduml block (handles AI outputting duplicates)
+          puml_match = re.search(r'(@start\w+.*?@end\w+)', code, re.DOTALL)
+          if puml_match:
+              code = puml_match.group(1)
+          else:
+              # No complete block found - ensure proper tags
+              if not code.strip().startswith('@start'):
+                  code = '@startuml\n' + code
+              if not code.strip().endswith('@enduml') and '@enduml' not in code:
+                  code = code + '\n@enduml'
 
-      print(code.strip())
+      elif format == 'mermaid':
+          # Extract first complete mermaid diagram (handles duplicates)
+          # Mermaid starts with diagram type declaration
+          mermaid_types = r'(graph|flowchart|sequenceDiagram|classDiagram|stateDiagram|erDiagram|gantt|pie|journey)'
+          mermaid_match = re.search(rf'({mermaid_types}[\s\S]*?)(?={mermaid_types}|\Z)', code)
+          if mermaid_match:
+              code = mermaid_match.group(1).strip()
+
+      result = code.strip()