Merge fix/gc-report-json-1257 into v5/json-envelope-unify

Keep the envelope ports of e2e_cargo and the Cargo GC contract text
(pruned entries are details.manifest events, so the preview key rename
on #1273 does not apply here).

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

Author: mikolalysenko