Four of seven review findings resolved. 5 new tests (391 -> 396 crate
tests; 438 -> 443 total). cargo test, clippy, wasm32 all green.
M2 (data_access.rs): write_bytes now validates data_len fits in u32
before the length-prefix cast. A >4GiB blob returns Access error
instead of silently writing a truncated length prefix (silent data
corruption on read-back).
M1 (builder.rs): Definitions::merge_into rewritten to access self.defs
directly instead of round-tripping through self.build() with a double-
cloned/unwrap_or_default chain that could silently drop definitions
on a shape mismatch. 4 new tests: insert-when-absent, merge-into-
existing, overwrite-duplicate-keys, no-op-on-non-object-top.
L1 (materialize.rs): byte-offset discriminator arm of
materialize_union_packed now uses checked_add for offset+disc_offset
and disc_abs_offset+disc_size, returning Access error on overflow.
Mirrors the existing sequential_reader.rs::read_union_value pattern.
L3 (error.rs): AlkTypeError::source() now returns Some(inner) for the
Validation variant (jsonschema::ValidationError implements
std::error::Error). Existing source_returns_none_for_all_variants
test split into source_returns_none_for_schema_offset_access and
source_returns_some_for_validation_variant.
Deferred: L2 (unreachable! -> Err, defense-in-depth), N1 (non-strict
RFC 3339 validator, docs-only), N2 (FieldValue::Bytes for Record,
API asymmetry). Review doc updated with resolution section.
glm-5.2
a975befdd1