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>

.github/skills/bmad-agent-tech-writer/mermaid-gen.md

@@ -0,0 +1,20 @@
+---
+name: mermaid-gen
+description: Create Mermaid-compliant diagrams
+menu-code: MG
+---
+
+# Mermaid Generate
+
+Create a Mermaid diagram based on user description through multi-turn conversation until the complete details are understood.
+
+## Process
+
+1. **Understand the ask** — Clarify what needs to be visualized
+2. **Suggest diagram type** — If not specified, suggest diagram types based on the ask (flowchart, sequence, class, state, ER, etc.)
+3. **Generate** — Create the diagram strictly following Mermaid syntax and CommonMark fenced code block standards
+4. **Iterate** — Refine based on user feedback
+
+## Output
+
+A Mermaid diagram in a fenced code block, ready to render.