feat: add Forgecode (forge) agent support

- Add 'forgecode' to AGENT_CONFIGS in agents.py with .forge/commands
  directory, markdown format, and {{parameters}} argument placeholder
- Add 'forgecode' to AGENT_CONFIG in __init__.py with .forge/ folder,
  install URL, and requires_cli=True
- Add forgecode binary check in check_tool() mapping agent key
  'forgecode' to the actual 'forge' CLI binary
- Add forgecode case to build_variant() in create-release-packages.sh
  generating commands into .forge/commands/ with {{parameters}}
- Add forgecode to ALL_AGENTS in create-release-packages.sh

.github/workflows/scripts/create-release-packages.sh

@@ -330,6 +330,9 @@ build_variant() {
     iflow)
       mkdir -p "$base_dir/.iflow/commands"
       generate_commands iflow md "\$ARGUMENTS" "$base_dir/.iflow/commands" "$script" ;;
+    forgecode)
+      mkdir -p "$base_dir/.forge/commands"
+      generate_commands forgecode md "{{parameters}}" "$base_dir/.forge/commands" "$script" ;;
     generic)
       mkdir -p "$base_dir/.speckit/commands"
       generate_commands generic md "\$ARGUMENTS" "$base_dir/.speckit/commands" "$script" ;;
@@ -339,7 +342,7 @@ build_variant() {
 }
 
 # Determine agent list
-ALL_AGENTS=(claude gemini copilot cursor-agent qwen opencode windsurf junie codex kilocode auggie roo codebuddy amp shai tabnine kiro-cli agy bob vibe qodercli kimi trae pi iflow generic)
+ALL_AGENTS=(claude gemini copilot cursor-agent qwen opencode windsurf junie codex kilocode auggie roo codebuddy amp shai tabnine kiro-cli agy bob vibe qodercli kimi trae pi iflow forgecode generic)
 ALL_SCRIPTS=(sh ps)
 
 validate_subset() {