feat(parser): handle inline comments in PEG command substitution

[lu-zero]

Exclude '#' from literal text when inside command context and add comment handling to command_piece() rule. This allows comments within
command substitutions to be properly parsed.

[github-actions]

Performance Benchmark Report

Benchmark name	Baseline (μs)	Test/PR (μs)	Delta (μs)	Delta %
clone_shell_object	17.07 μs	16.96 μs	-0.11 μs	⚪ Unchanged
eval_arithmetic	0.15 μs	0.15 μs	0.00 μs	⚪ Unchanged
expand_one_string	1.52 μs	1.53 μs	0.01 μs	⚪ Unchanged
for_loop	22.30 μs	22.61 μs	0.31 μs	⚪ Unchanged
full_peg_complex	58.05 μs	58.37 μs	0.32 μs	⚪ Unchanged
full_peg_for_loop	6.13 μs	6.14 μs	0.01 μs	⚪ Unchanged
full_peg_nested_expansions	16.64 μs	16.87 μs	0.23 μs	⚪ Unchanged
full_peg_pipeline	4.24 μs	4.18 μs	-0.05 μs	⚪ Unchanged
full_peg_simple	1.78 μs	1.76 μs	-0.01 μs	⚪ Unchanged
function_call	2.10 μs	2.12 μs	0.02 μs	⚪ Unchanged
instantiate_shell	52.37 μs	52.74 μs	0.38 μs	⚪ Unchanged
instantiate_shell_with_init_scripts	25198.47 μs	25512.83 μs	314.36 μs	⚪ Unchanged
parse_peg_bash_completion	2051.25 μs	2062.65 μs	11.40 μs	🟠 +0.56%
parse_peg_complex	19.70 μs	19.03 μs	-0.67 μs	🟢 -3.39%
parse_peg_for_loop	2.00 μs	1.98 μs	-0.02 μs	⚪ Unchanged
parse_peg_pipeline	2.07 μs	2.00 μs	-0.06 μs	🟢 -3.14%
parse_peg_simple	1.09 μs	1.07 μs	-0.02 μs	⚪ Unchanged
run_echo_builtin_command	15.27 μs	15.33 μs	0.06 μs	⚪ Unchanged
tokenize_sample_script	3.46 μs	3.42 μs	-0.04 μs	⚪ Unchanged

Code Coverage Report: Only Changed Files listed

Package	Base Coverage	New Coverage	Difference
brush-core/src/commands.rs	🟢 91.52%	🟢 91.74%	🟢 0.22%
brush-core/src/results.rs	🟢 80.16%	🟢 83.33%	🟢 3.17%
brush-interactive/src/basic/input_backend.rs	🟠 60%	🟠 62.86%	🟢 2.86%
brush-parser/src/word.rs	🟢 93.5%	🟢 93.52%	🟢 0.02%
Overall Coverage	🟢 73.41%	🟢 73.45%	🟢 0.04%

Minimum allowed coverage is 70%, this run produced 73.45%

Test Summary: bash-completion test suite

Outcome	Count	Percentage
✅ Pass	1563	74.11
❗️ Error	18	0.85
❌ Fail	174	8.25
⏩ Skip	339	16.07
❎ Expected Fail	13	0.62
✔️ Unexpected Pass	2	0.09
📊 Total	2109	100.00

[reubeno]

I ran the 2 added YAML tests without the fix:

• Comment in command substitution without newline fails - it does indeed fail, just with a different error than bash (so I'd expect the test to pass with ignore_stderr: true)
• Comment in command substitution with newline - passes even without any code changes

Can you identify what case, in particular, you believe is a problem in the current code base?

[lu-zero]

If it passes without the change, it is just me repeating the fix I had to make in winnow, but that's strange I was quite sure the original from Gentoo failed even with the stand alone tokenizer...

[lu-zero]

we can just keep the tests and consider later that bit if we want to emit comments and keep the peg parser