chore(release): Nexus Unity 1.6.0

[Daliys]

Release 1.6.0

This signed release commit promotes the reviewed development work onto the current main baseline.

Highlights

• bounded UI hierarchy, query, and snapshot traversal
• non-blocking WebSocket handling and persistent MCP authentication
• safer destructive asset operations, path/type handling, PlayerPrefs, and scene dependency behavior
• stronger editor readiness, test-result, and focus handling

Validation

• 43 Python bridge tests passed
• 11 Unity integration suites / 355 checks passed
• live MCP smoke verified 117 raw tools and 14 consolidated manager tools

See CHANGELOG.md for complete release notes.