Add CI and lock script regressions

[Xcodes-chain]

Summary

Adds a PR validation structure for Fiber scripts and expands contract regression coverage.

• Adds fmt-check and pr-verify Makefile targets.
• Extends CI to run format and clippy before reproducible build and tests.
• Adds CI workflow guard tests so required PR validation layers are not accidentally removed.
• Adds FundingLock negative regressions for multiple group inputs, malformed witness args, and wrong signatures.
• Adds a CommitmentLock stale revocation version regression.
• Updates scripts/find_clang to skip Apple clang, which reports a high version but cannot build the CKB RISC-V target.

Validation

• cargo fmt --check
• make clippy CARGO_ARGS="--all-targets"
• cargo test -p tests ci_workflow
• cargo test -p commitment-lock test_mul

Notes

make build could not be completed on the local macOS environment because it lacks non-Apple LLVM clang 16+ / RISC-V C compiler support and Docker. The CI workflow still runs the reproducible Docker build.