refactor(ecstore): retire the set_disk lint blankets by making the prelude explicit
backlog#1823 step 1 / backlog#2029 road 2. Removes the last two module-level lint blankets in ecstore: set_disk/mod.rs #![allow(unused_imports)] and #![allow(unused_variables)], restoring both lints for the whole 40K-line subtree, and deletes the register line for the unused_variables blanket in the same diff (the guard from #6155 is a bidirectional exact match).
The unused_imports blanket existed because 14 submodules consumed mod.rs as a glob prelude (use super::* / use super::super::*), and rustc does not track consumption through glob re-exports. Each glob is now an explicit use super::{...} list, keeping mod.rs as the single import hub while making every import lint-checkable. Names consumed only by test or test-util units carry #[cfg(test)] / #[cfg(all(test, feature = "test-util"))] / #[cfg(any(test, feature = "test-util"))] gates matching their consumers; storage-api traits are routed through the storage_api_contracts facade per the architecture guard.
The sweep then deleted the genuinely dead imports the blanket was hiding (chrono::Utc, glob::Pattern, futures::task::AtomicWaker, rustfs_lock LocalLock, AsyncBatchProcessor, rand::Rng, std::future::Future among others in mod.rs, plus stale scoped imports and one empty test module shell across the subtree). One unused_variables finding surfaced: flush_read_version_coalescer_pending's lane_key is read only by the #[cfg(test)] counter block, handled with the cfg(not(test)) let _ pattern established in #6158.
Verification: cargo check zero warnings versus the 9cf276ed2 baseline on five lanes (default lib / --tests / rio-v2 --tests / test-util --tests / test-util,rio-v2 --tests; the --tests lane keeps the same three pre-existing core/pools.rs and store/object.rs dead-code warnings main already has); clippy --lib --tests -D warnings clean with test-util,rio-v2; cargo nextest run 4567 passed; make pre-commit exit 0.
Add a deterministic transition matrix case for a stale prepared metadata snapshot followed by a committed transition, duplicate transition, and late GET. The test proves the stale metadata generation is physically reclaimed, duplicate transition does not upload a second remote candidate, and the late GET reads the committed remote body byte-for-byte instead of reopening the released local source.
Refs rustfs/backlog#1355
Co-authored-by: heihutu <heihutu@gmail.com>
Zhengchao An