chore: add BMAD workflow commands for Claude and Cursor

Include .claude/commands/ and .cursor/commands/ containing all BMAD
workflow definitions so team members can use them out of the box.
Only .claude/settings.local.json remains gitignored (user-specific).

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

.claude/commands/bmad-index-docs.md

@@ -0,0 +1,10 @@
+---
+name: 'index-docs'
+description: 'Generates or updates an index.md to reference all docs in the folder. Use if user requests to create or update an index of all files in a specific folder'
+---
+
+# index-docs
+
+Read the entire task file at: {project-root}/_bmad/core/tasks/index-docs.xml
+
+Follow all instructions in the task file exactly as written.