chore(blend-adapter): replace expect() with typed ContractError in accrue

[Adecom16]

Closes #459

Summary

• Replace expect() calls in accrue() with typed ContractError propagation.
• Update accrue() to return Result<(), ContractError>.
• Preserve existing contract behavior while aligning with the project's error-handling conventions.
• Update affected tests and call sites where necessary.

Test plan

• cargo fmt --all -- --check
• cargo clippy --all-targets -- -D warnings
• cargo test

[vercel]

@Adecom16 is attempting to deploy a commit to the Collins' projects Team on Vercel.

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[collinsezedike]

The code is correct and matches #459's plan: both .expect() calls are replaced with ContractError::Overflow, accrue() now returns Result<(), ContractError>, existing tests updated to try_accrue(), and a new test exercises the overflow path directly rather than just changing the signature without covering it.

CI is failing on Commit Messages: the header "chore(blend-adapter): replace expect() with typed ContractError in accrue" is 73 characters, over the 72-character limit. Shorten it and push.

[Adecom16]

Hi @collinsezedike, I've updated the commit message to meet the 72-character limit and pushed the changes. The requested change has been addressed. Thanks!

The code is correct and matches #459's plan: both .expect() calls are replaced with ContractError::Overflow, accrue() now returns Result<(), ContractError>, existing tests updated to try_accrue(), and a new test exercises the overflow path directly rather than just changing the signature without covering it.

CI is failing on Commit Messages: the header "chore(blend-adapter): replace expect() with typed ContractError in accrue" is 73 characters, over the 72-character limit. Shorten it and push.

[collinsezedike]

Header's fixed and CI is green. The fix itself was already verified: correctly collapses both .expect() calls into ContractError::Overflow, accrue() returns Result<(), ContractError>, tests updated to try_accrue(), and the new accrue_returns_typed_error_on_overflow test exercises the overflow path directly.

Thank you for sticking with this through the review back-and-forth.

Merging now.