chore: remove BMAD framework files and IDE configuration artifacts

Clean up unused BMAD workflow, agent, and command files across all IDE
configurations (.agent, .clinerules, .cursor, .gemini, .github, .kilocode,
.opencode) and internal module files (_bmad/bmb, _bmad/bmm).

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

.opencode/skills/bmad-create-architecture/architecture-decision-template.md

@@ -0,0 +1,12 @@
+---
+stepsCompleted: []
+inputDocuments: []
+workflowType: 'architecture'
+project_name: '{{project_name}}'
+user_name: '{{user_name}}'
+date: '{{date}}'
+---
+
+# Architecture Decision Document
+
+_This document builds collaboratively through step-by-step discovery. Sections are appended as we work through each architectural decision together._