fix: handle expansion in here documents

[reubeno]

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[github-actions]

Performance Benchmark Report

Benchmark name	Baseline (μs)	Test/PR (μs)	Delta (μs)	Delta %
expand_one_string	3.42 μs	3.42 μs	-0.00 μs	⚪ Unchanged
instantiate_shell	59.88 μs	60.72 μs	0.84 μs	⚪ Unchanged
instantiate_shell_with_init_scripts	28124.08 μs	27846.01 μs	-278.08 μs	🟢 -0.99%
parse_bash_completion	2649.46 μs	2738.85 μs	89.39 μs	🟠 +3.37%
parse_sample_script	3.83 μs	4.02 μs	0.19 μs	🟠 +4.91%
run_echo_builtin_command	90.58 μs	91.19 μs	0.61 μs	⚪ Unchanged
run_one_builtin_command	109.95 μs	108.94 μs	-1.02 μs	⚪ Unchanged
run_one_external_command	1981.14 μs	1912.48 μs	-68.66 μs	🟢 -3.47%
run_one_external_command_directly	1013.79 μs	1010.08 μs	-3.71 μs	⚪ Unchanged

Code Coverage Report: Only Changed Files listed

Package	Base Coverage	New Coverage	Difference
brush-parser/src/tokenizer.rs	🟢 96.27%	🟢 96.48%	🟢 0.21%
Overall Coverage	🟢 75.48%	🟢 75.56%	🟢 0.08%

Minimum allowed coverage is 70%, this run produced 75.56%