[MCA Inspector] Research & evaluate NBT libraries

## Summary

Evaluate NBT (Named Binary Tag) libraries for reading Minecraft region files. Select the best candidate for the MCA Inspector project.

## Candidates to Evaluate

- **fNbt** — Most widely used, MIT license, good documentation
- **SharpNBT** — Alternative implementation
- **Unmined.Minecraft.Nbt** — Specialized for Minecraft tools

## Research Tasks

- [ ] Verify MIT license compatibility
- [ ] Test reading real .mca region file from itzg Docker image
- [ ] Benchmark read performance (load time, query latency)
- [ ] Document required API shape
- [ ] Verify Minecraft 1.20+ chunk format support

## Deliverables

- Clear recommendation + reasoning
- Sample code reading blocks from test .mca file
- Performance numbers
- Any limitations documented

## Acceptance Criteria

- [ ] Clear NBT library recommendation
- [ ] Sample code demonstrates the API
- [ ] Performance baseline established
- [ ] Ready to proceed with project creation

Evaluate fNbt, SharpNBT, and Unmined.Minecraft.Nbt, starting with MIT license compatibility and support for Minecraft 1.20+ chunk data. Use a real .mca region file from the itzg Docker image to test block reads and benchmark load time and query latency. Done means a documented recommendation, sample API code, performance baseline, and limitations.

Written by the indexing model from the issue text.