Migration checks

The package UPGRADE guide is the canonical consumer migration document. It contains the before/after changes for the 0.4 release, session isolation correction #288, response finalization, bounded emitter buffers, and historical class renames. Do not maintain a separate migration checklist here.

Start with the installed version and the application’s runner, then use configuration for session and cookie settings and practical examples for the emission/finalization pattern. Report validation of each affected integration point and any server runtime that was not exercised.