* fix(DBDriver): resolve lock-order inversion between dbSafeAccess and trashes mutexes
emptyTrashes() acquired _dbSafeAccessMutex while holding _trashesMutex
(M1->M0), whereas the load() path acquires _dbSafeAccessMutex and then,
inside loadQuery()->getLastWordId(), acquires _trashesMutex (M0->M1).
This opposite nesting forms a lock-order cycle that ThreadSanitizer flags
as a potential deadlock.
Acquire _dbSafeAccessMutex only after releasing _trashesMutex, matching
the sequential 'look in trash, then database' pattern used by every other
DBDriver accessor (getLastWordId, getLastMapId, getInvertedIndexNi, ...).
Refs: #1765
* Fxing the actual deadlock
* Added doc
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Co-authored-by: matlabbe <[email protected]>
