fix: better handle escape chars in pattern bracket exprs

[reubeno]

No description provided.

[github-actions]

Test Results

    2 files      9 suites   1m 12s ⏱️
  527 tests   527 ✅ 0 💤 0 ❌
1 042 runs  1 042 ✅ 0 💤 0 ❌

Results for commit 1ccaac7.

[github-actions]

Performance Benchmark Report

Benchmark name	Baseline (μs)	Test/PR (μs)	Delta (μs)	Delta %
expand_one_string	3.43 μs	3.43 μs	0.00 μs	⚪ Unchanged
instantiate_shell	60.76 μs	60.92 μs	0.16 μs	⚪ Unchanged
instantiate_shell_with_init_scripts	30046.13 μs	30464.64 μs	418.51 μs	⚪ Unchanged
parse_bash_completion	2817.80 μs	2861.85 μs	44.05 μs	🟠 +1.56%
parse_sample_script	4.20 μs	4.39 μs	0.19 μs	⚪ Unchanged
run_echo_builtin_command	90.70 μs	92.73 μs	2.02 μs	🟠 +2.23%
run_one_builtin_command	107.35 μs	109.92 μs	2.57 μs	⚪ Unchanged
run_one_external_command	1993.90 μs	1965.70 μs	-28.20 μs	🟢 -1.41%
run_one_external_command_directly	1008.31 μs	1009.07 μs	0.76 μs	⚪ Unchanged

Code Coverage Report: Only Changed Files listed

Package	Base Coverage	New Coverage	Difference
brush-core/src/expansion.rs	🟢 96.53%	🟢 96.26%	🔴 -0.27%
brush-core/src/patterns.rs	🟢 97.78%	🟢 97.92%	🟢 0.14%
brush-core/src/regex.rs	🟢 97.67%	🟢 100%	🟢 2.33%
Overall Coverage	🟢 74.57%	🟢 74.58%	🟢 0.01%

Minimum allowed coverage is 70%, this run produced 74.58%