fix: propagate execution parameters more thoroughly

[reubeno]

Address cases where command substitution environments don't correctly inherit the open files of the containing command.

Caveat: I'm not thrilled about how much code needed to be touched, but this at least fixes a known defect. Hopefully we can clean it up subsequently.

Copilot reviewed 5 out of 10 changed files in this pull request and generated no comments.

Files not reviewed (5)

• brush-core/src/interp.rs: Evaluated as low risk
• brush-core/src/arithmetic.rs: Evaluated as low risk
• brush-core/src/extendedtests.rs: Evaluated as low risk
• brush-shell/tests/cases/redirection.yaml: Evaluated as low risk
• brush-core/src/builtins/printf.rs: Evaluated as low risk

[github-actions]

Test Results

    2 files      9 suites   1m 46s ⏱️
  668 tests   668 ✅ 0 💤 0 ❌
1 322 runs  1 322 ✅ 0 💤 0 ❌

Results for commit 1bac20b.

♻️ This comment has been updated with latest results.

[github-actions]

Performance Benchmark Report

Benchmark name	Baseline (μs)	Test/PR (μs)	Delta (μs)	Delta %
clone_shell_object	17.99 μs	18.07 μs	0.08 μs	🟠 +0.46%
eval_arithmetic	0.17 μs	0.17 μs	0.00 μs	⚪ Unchanged
expand_one_string	1.71 μs	1.81 μs	0.10 μs	⚪ Unchanged
for_loop	22.69 μs	21.80 μs	-0.89 μs	🟢 -3.94%
function_call	2.78 μs	2.33 μs	-0.46 μs	🟢 -16.36%
instantiate_shell	57.00 μs	57.43 μs	0.43 μs	⚪ Unchanged
instantiate_shell_with_init_scripts	23038.14 μs	20391.56 μs	-2646.58 μs	🟢 -11.49%
parse_bash_completion	1669.90 μs	1649.69 μs	-20.21 μs	🟢 -1.21%
parse_sample_script	1.74 μs	1.77 μs	0.03 μs	🟠 +1.61%
run_echo_builtin_command	16.00 μs	15.24 μs	-0.77 μs	⚪ Unchanged
run_one_external_command	2393.14 μs	2359.33 μs	-33.81 μs	⚪ Unchanged
tokenize_sample_script	2.78 μs	2.82 μs	0.03 μs	🟠 +1.22%

Code Coverage Report: Only Changed Files listed

Package	Base Coverage	New Coverage	Difference
brush-core/src/arithmetic.rs	🟢 98.48%	🟢 98.52%	🟢 0.04%
brush-core/src/builtins/printf.rs	🟢 93.88%	🟢 94.55%	🟢 0.67%
brush-core/src/builtins/test.rs	🟢 91.3%	🟢 92.59%	🟢 1.29%
brush-core/src/commands.rs	🟢 87.14%	🟢 87.21%	🟢 0.07%
brush-core/src/completion.rs	🟠 63.43%	🟠 63.41%	🔴 -0.02%
brush-core/src/expansion.rs	🟢 96.1%	🟢 96.14%	🟢 0.04%
brush-core/src/extendedtests.rs	🟠 64.61%	🟠 66.46%	🟢 1.85%
brush-core/src/interp.rs	🟢 91.48%	🟢 91.58%	🟢 0.1%
brush-core/src/options.rs	🟢 92.39%	🟢 93.48%	🟢 1.09%
brush-core/src/shell.rs	🟢 86.07%	🟢 85.95%	🔴 -0.12%
brush-core/src/sys/unix/signal.rs	🟠 64.41%	🟠 61.02%	🔴 -3.39%
brush-core/src/tests.rs	🟠 50%	🟠 52.63%	🟢 2.63%
Overall Coverage	🟢 77.81%	🟢 77.88%	🟢 0.07%

Minimum allowed coverage is 70%, this run produced 77.88%