Fix CmdArgBuffer SERIALIZED_SIZE computation

[Sarah5567]

Related Issue(s)	#4896
Has Unit Tests (y/n)	n
Documentation Included (y/n)	n
Generative AI was used in this contribution (y/n)	y

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Change Description

Fix CmdArgBuffer::SERIALIZED_SIZE, which incorrectly used sizeof(I32) instead of sizeof(FwSizeStoreType).
To prevent this kind of mistake, this PR adds a STATIC_SERIALIZED_SIZE constexpr helper to LinearBufferBase and updates all buffer-derived classes to use it.

Rationale

If FwSizeStoreType is configured larger than I32 (e.g. U64), CmdArgBuffer::SERIALIZED_SIZE would be too small, potentially causing serialization issues.

Testing/Review Recommendations

N/A

Future Work

N/A

AI Usage (see policy)

GitHub Copilot CLI (Claude)

[LeStarch]

To fix the formatting, you can run this command:

git diff --name-only devel...HEAD | fprime-util format --stdin