docs: document adapter 1.1.0 setup

[uz0r]

Summary

Updates the PurrNet Dissonance adapter README for version 1.1.0:

• documents the official Package Manager Git URL;
• adds the required Unity and Dissonance setup steps;
• explains automatic startup and planned-role selection;
• documents manual initialization through TryRunManually();
• documents the opt-in startServerAsHost promotion flow;
• records the current validation scope and remaining standalone/headless test gap.

Dependency

This documentation describes the lifecycle and reconnect behavior introduced in #6.

It intentionally contains README changes only and should be merged after #6.

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