Align the identity predicate with the ratified shape-only rule

Accept liberally, emit conservatively (764a4d4): the gate is 8-4-4-4-12
hex in any case and any UUID version — uuidgen and UUID().uuidString
print uppercase, and a strict lowercase gate would silently stray an
agent's standard-tool card. Identity comparison is UUID-value equality
everywhere: ItemID keeps its byte-faithful rawValue but equates and
hashes on the lowercased canonical form, and the writer's
import-boundary collision check canonicalizes, so a same-UUID arrival
spelled in another case remints instead of slipping past. The app still
mints only lowercase v4 and never renames to canonicalize.

Full suite 342 tests in 63 suites green. Two findings filed.

Claude-Session: https://claude.ai/code/session_018BjQRYBR6jQja3jCRi5S3A

Fixtures/README.md

@@ -4,7 +4,7 @@ Golden fixture boards for the storage-contract test suite — real on-disk folde
 
 Bundled into the unit-test target as a folder reference (see `project.yml`). Valid boards live under `Valid/`, fail-fast cases under `Malformed/`. Tests live in `KanbanTests/FixtureBoardTests.swift`.
 
-Lane/card folder names are fixed literal lowercase-UUIDv4-shaped strings (never generated at test time), chosen so their lexicographic order matches the expected tie-break order — usually a leading digit (`10000000-...`, `20000000-...`, …) so folder order reads the same as array-index order in the tests.
+Lane/card folder names are fixed literal lowercase-UUIDv4-shaped strings (never generated at test time), chosen so their lexicographic order matches the expected tie-break order — usually a leading digit (`10000000-...`, `20000000-...`, …) so folder order reads the same as array-index order in the tests. That is a fixture-authoring convention, not the loader's gate: the identity predicate is shape-only (`8-4-4-4-12` hex, **any case, any version** — 01-storage-format.md § Fractal layout ▸ Rules), and the case/version coverage lives in `KanbanTests/BoardLoaderTests.swift` rather than here.
 
 ## Valid/ — one board per tolerated/valid case