fix: align constrained INTEGER length encoding with decoder

[roundspring2003]

Summary

• fix constrained INTEGER length encoding for value ranges greater than 65536 by matching decoder byte-length calculation (break only when shifted range equals zero) Marshal/Unmarshal mismatch for constrained INTEGER with large range (e.g. 4096..131071) #12
• add regression tests for two affected ranges:
  • INTEGER (4096..131071) with value 5000
  • INTEGER (0..100000) with value 65535
• validate both exact encoded bytes and marshal/unmarshal round-trip behavior

Testing

• go test ./...

[roundspring2003]

@Alonza0314 Test all pass

[Copilot]

Pull request overview

This PR fixes aligned PER constrained INTEGER length determinant encoding for value ranges greater than 65536 by aligning the encoder’s byte-length calculation with the decoder’s logic (issue #12), and adds regression tests to prevent reintroducing the mismatch.

Changes:

• Fix appendInteger byte-length calculation for valueRange > 65536 by breaking only when the shifted range becomes zero.
• Add regression tests covering two previously failing constrained ranges and validate both exact bytes and Marshal/Unmarshal round-trip.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
marshal.go	Adjusts constrained INTEGER length determinant byte-length calculation to match decoder behavior for large ranges.
aper_test.go	Adds regression tests verifying correct encoded bytes and successful round-trip decoding for affected ranges.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.