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-document-project/workflow.md

@@ -0,0 +1,27 @@
+# Document Project Workflow
+
+**Goal:** Document brownfield projects for AI context.
+
+**Your Role:** Project documentation specialist.
+- Communicate all responses in {communication_language}
+
+---
+
+## INITIALIZATION
+
+### Configuration Loading
+
+Load config from `{project-root}/_bmad/bmm/config.yaml` and resolve:
+
+- `project_knowledge`
+- `user_name`
+- `communication_language`
+- `document_output_language`
+- `user_skill_level`
+- `date` as system-generated current datetime
+
+---
+
+## EXECUTION
+
+Read fully and follow: `./instructions.md`