* Add Power BI resources: 4 chat modes, 6 instructions, 4 prompts, and resources README
* Remove power-bi-resources-README.md - not needed for PR
* Add Power BI Development collection
* Fix PR review feedback: Add collection YAML file and remove double fenced code blocks
- Add power-bi-development.collection.yml with proper metadata
- Remove outer 4-backtick fences from all Power BI files (chatmodes, instructions, prompts)
- Files now have only the standard 3-backtick fences for proper GitHub Copilot compatibility
* Remove outer code fences from Power BI chatmode files
