Publish client-owned side state after retained surfaces and roll it back in reverse order on any transaction failure.\n\nVerified: 715 ERT tests, 92 doctests, WERROR compile-all, checkdoc, git diff --check.
Introduce pure retained plans, stable objects, marker-backed range ownership, side indexes, content/property diffs, and multi-buffer rollback as the generic publication runtime. Verification: 707 ERT tests; 92 doctests; shuffled seed 20260806; compile-all WERROR=t.
