chore: remove dead commented util code

[kitsuyui]

Summary

• Remove the commented-out deep_clone_* helper block from src/util.rs.
• Keep the active utility helpers unchanged.

Verification

• cargo fmt --all -- --check
• cargo clippy --all-targets --all-features -- -D warnings
• cargo check
• cargo test --all-targets --all-features
• cargo test --all-features
• cargo build --release --all-features
• scripts/test-check-cargo-version-tag.sh
• git diff --check

spellcheck and octocov depend on GitHub Actions reusable workflow/token behavior and will be verified by CI.

[github-actions]

Code Metrics Report

	main (0c91c43)	#120 (482efa1)	+/-
Coverage	68.3%	68.3%	0.0%
Code to Test Ratio	1:0.1	1:0.1	0.0
Test Execution Time	3s	4s	+1s

Details

  |                     | main (0c91c43) | #120 (482efa1) | +/-  |
  |---------------------|----------------|----------------|------|
  | Coverage            |          68.3% |          68.3% | 0.0% |
  |   Files             |              4 |              4 |    0 |
  |   Lines             |            550 |            550 |    0 |
  |   Covered           |            376 |            376 |    0 |
  | Code to Test Ratio  |          1:0.1 |          1:0.1 |  0.0 |
  |   Code              |            593 |            593 |    0 |
  |   Test              |             71 |             71 |    0 |
- | Test Execution Time |             3s |             4s |  +1s |

Code coverage of files in pull request scope (58.8% → 58.8%)

Files	Coverage	+/-	Status
src/util.rs	58.8%	0.0%	modified

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Reported by octocov