CUBELinux-2
49698af9fc
open() derived the delta path as "${db_path}.delta" (e.g. "db3.json.delta")
while checkpoint_store() writes via db_path.with_extension("delta")
(e.g. "db3.delta"). On reopen, load_base_plus_delta therefore read a
never-written path and silently skipped the delta, so post-checkpoint
changes were lost. Use db_p.with_extension("delta") in both places.
Also drop a no-op cp_seq.max(0) (u64 >= 0 always) to clear the clippy
-W clippy::unnecessary_min_or_max lint.
Verified: ./check all green; incremental_checkpoint_delta_model,
durable_checkpoint_and_replay, wal_recovery_after_crash pass in isolation.