feat(contract): implement cargo-fuzz testing for register and execute (#98)

[MarcusDavidG]

Summary

Closes #98

Implements fuzz testing for the SoroTask smart contract using cargo-fuzz (libFuzzer), targeting the two core functions: register and execute.

Changes

New: contract/fuzz/

• fuzz_targets/fuzz_register.rs — drives register() with randomized interval and gas_balance bytes. Asserts that interval == 0 always panics with InvalidInterval and that any non-zero interval never causes an unexpected panic.
• fuzz_targets/fuzz_execute.rs — drives execute() with randomized interval, ledger timestamp, and gas_balance. Catches any unexpected panics outside of the known error variants.

Modified: contract/Cargo.toml

• Added rlib to crate-type so the fuzz harness can link against the contract as a library.

Fixed: contract/src/lib.rs

• Fixed a pre-existing missing closing brace in resume_task() that was causing a compile error.

Updated: contract/README.md

• Added a Fuzz Testing section documenting prerequisites, available targets, how to run locally, and how to reproduce crashes.

How to run

cd contract

# Fuzz register
cargo +nightly fuzz run fuzz_register

# Fuzz execute
cargo +nightly fuzz run fuzz_execute

# With a time limit
cargo +nightly fuzz run fuzz_register -- -max_total_time=60

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@MarcusDavidG Great news! 🎉 Based on an automated assessment of this PR, the linked Wave issue(s) no longer count against your application limits.

You can now already apply to more issues while waiting for a review of this PR. Keep up the great work! 🚀

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[ayomideadeniran]

Pr under review.