fix: list non-ascii as octal bytes

[MukundaKatta]

Summary

• update the l command to emit non-ASCII UTF-8 bytes as three-digit octal escapes
• keep existing named escapes and printable ASCII output unchanged
• update the Unicode listing fixture and add a regression for the reported cÃ🧰y case

Fixes #249.

Tests

• printf 'cÃ🧰y\n' | cargo run --quiet -- -e 'l'
• cargo test list_unicode
• cargo test list_non_ascii_uses_octal_bytes
• cargo fmt --check
• git diff --check
• cargo test test_sed
• cargo test

[codecov]

Codecov Report

❌ Patch coverage is 0% with 5 lines in your changes missing coverage. Please review.
✅ Project coverage is 82.16%. Comparing base (f083fa0) to head (7a24f4f).
⚠️ Report is 6 commits behind head on main.

Files with missing lines	Patch %	Lines
src/sed/processor.rs	0.00%	5 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #436      +/-   ##
==========================================
- Coverage   82.20%   82.16%   -0.05%     
==========================================
  Files          13       13              
  Lines        5542     5545       +3     
  Branches      310      309       -1     
==========================================
  Hits         4556     4556              
- Misses        983      986       +3     
  Partials        3        3              

Flag	Coverage Δ
macos_latest	82.85% <0.00%> (-0.05%)	⬇️
ubuntu_latest	82.95% <0.00%> (-0.05%)	⬇️
windows_latest	0.00% <0.00%> (ø)

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[codspeed-hq]

Merging this PR will not alter performance

✅ 11 untouched benchmarks

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_{Comparing MukundaKatta:codex/list-nonascii-octal (7a24f4f) with main (a65af95)}