Final low-severity items from the re-review of ee10f932.
L2: DbUpdateConcurrencyException derives from DbUpdateException but carries no
provider exception, so IsUniqueConstraintViolation does not classify it. A row
deleted by a concurrent library edit between the heal's read and its save would
propagate and fail the scan, contradicting the invariant stated directly above
it. Admit it in the filter.
L1: lift the in-memory ordinal settle into LibraryRepository.ResolveExact and
unit-test it with both spellings in the candidate list. No SQLite-backed test
can exercise it (SQLite's = on TEXT is already binary), so this converts the
half that rested on hand-run MySQL evidence into automated coverage. The
end-to-end companion test's comment no longer claims to be provider-independent.
L4: assert PRAGMA foreign_keys is 1 before migrating, so the enforcement guard
cannot silently degrade into the weak pre-fix form it was added to replace.
L3: detach the failed heal, matching the insert path.
N3: the heal's inner predicate now matches its IsNullOrEmpty outer guard, so a
PathHash = '' row cannot enter the branch and silently never heal.
N4: record that GetFolder returning null for a case-differing spelling makes
MySQL insert a second row where it used to reuse one — correct, and now matching
SQLite, but a real behaviour change on a case-insensitive filesystem.
Refs #488#308fix#491
timothy
ecb763ea58