Fix host initialization and reconnect lifecycle

[uz0r]

Summary

Fixes several lifecycle issues in the PurrNet Dissonance adapter:

• Prevents a host client from being registered with PurrNet's transient Server player ID.
• Starts voice from PurrNet lifecycle events with state catch-up, so initialization does not depend on Unity component order.
• Use PurrNet's ShouldStart predicate for consistent editor, clone, build, and disabled-flag behavior.
• Removes departed clients from the Dissonance server and clears queued packets on session transitions, fixing reconnect failures caused by stale peers or session IDs.
• Keeps the Dissonance server alive when only a host's local client disconnects.
• Adds startServerAsHost for the opt-in server-to-host promotion flow; normal role selection follows PurrNet's planned or actual host role.
• Replaces Unity's deprecated FindObjectOfType usage.

Validation

Tested in Unity 6000.4 Multiplayer Play Mode 2.0.2 with PurrNet v1.20.0-beta.249 and Dissonance 9.0.9:
host/client connection, disconnect, reconnect, and server-to-host promotion.

Standalone and headless dedicated-server builds still need explicit validation.

Full notes can be checked here https://github.com/uz0r/PurrNet-Dissonance/blob/docs/fork-changes/ADAPTER-REFACTOR-NOTES.md

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