In `@crates/compiler-core/src/bytecode/oparg.rs`:
- Around line 288-303: The TryFrom<u32> impl for MakeFunctionFlags currently
uses a silent truncating cast (value as u8); change MakeFunctionFlags::try_from
to perform a checked conversion (use u8::try_from(value) and map any Err to
MarshalError::InvalidBytecode) and then call Self::from_bits on the resulting
u8, returning the same InvalidBytecode error if from_bits returns None; update
references in the impl TryFrom<u32> for MakeFunctionFlags to remove the direct
cast and use the checked conversion pattern used elsewhere (e.g., instruction
parsing) so high-bit values are rejected instead of truncated.

In `@crates/compiler-core/src/bytecode/oparg.rs`:
- Around line 567-580: Replace the infallible From<u32> for UnpackExArgs with a
checked TryFrom<u32> implementation that validates the top two bytes are zero
and returns an appropriate error on non-zero high bits; keep the existing
From<UnpackExArgs> for u32 as-is and ensure UnpackExArgs still implements
OpArgType (update any call sites to use TryFrom::try_from where needed).
Specifically, implement TryFrom<u32> for UnpackExArgs by calling
value.to_le_bytes(), verifying that bytes[2] and bytes[3] are zero, and
constructing Self { before: bytes[0], after: bytes[1] } on success, otherwise
return an error consistent with the crate's error type pattern (matching how
MakeFunctionFlags handles malformed input).

In `@crates/compiler-core/src/bytecode/oparg.rs`:
- Around line 186-195: ResumeType is missing the standard enum boilerplate used
elsewhere: add the impl_oparg_enum_traits! macro invocation for ResumeType and
provide the OpArgType impl for ResumeType (matching the pattern used by
RaiseKind, IntrinsicFunction1, IntrinsicFunction2, etc.) so it can be treated as
an instruction argument; locate the ResumeType enum and insert
impl_oparg_enum_traits!(ResumeType) and the corresponding impl OpArgType for
ResumeType following the same structure as the other enums in this file.