fix(cluster): stabilize MVP transaction and read completion

[sqlrush]

Correctness maintenance v0.130.1 from v0.130.0. No experimental performance scheduling, workload relaxation, timeout increase, protocol-format or disk-format changes. Fixes cover CR refusal/dependency completion, exact transaction cancellation, nested UPDATE receipt and slot lifecycles, lock cancellation bookkeeping, statement visibility, and safe shared-read retry/error cleanup. Original PRE on kernel 24e752c passed all four samples: zero unexpected client/server errors, complete four-node million-row comparisons, health/debt checks, and native clean shutdown. Local registered C suite: 311 binaries passed. Measured TPS: 568.54 / 523.88 / 238.71 / 284.89; median 404.385, not a claimed performance gain. Release metadata and user documentation are the only changes after the tested kernel. All five PR checks and all seven exact-commit MVP release checks passed before merge. Initial macOS unit failures remain recorded; unchanged reruns passed without claiming a root-cause fix. Merged into main as 2c57b94 after the explicitly authorized one-time human approval bypass; no CI gate was waived. Immutable v0.130.1 points to qualified head 30a86ae. Tag Fast35365260736 and MVP35365260728 passed all seven required jobs; main Fast35365209903 passed all five. Published source maintenance release: https://github.com/sqlrush/pgrac/releases/tag/v0.130.1 . Exact-tag CI evidence is attached to the release. Old stable tag and failed evidence are preserved.