feat(completion): progress toward passing bash-completion test suite

[reubeno]

These changes are an assortment focused on being able to run the bash-completion pytest/pexpect-based test suite and increase our pass rate of its tests. Along the way a number of targeted fixes and additions were made to address compatibility issues identified as side effects of these tests.

Upon initial execution of the tests we saw:

447 failed, 1043 passed, 381 skipped, 18 xfailed, 174 errors in 2361.74s (0:39:21)

(xfailed means "expected failed".) I haven't done a full re-run of the tests, but expected the pass rate to be somewhat higher with these changes.

Notable changes:

• Overhaul of the "basic" input backend to support tab completion, and further, to support programmatic testing via pexpect and other standard pty-based testing frameworks. This required a fair bit of fiddling to avoid use of VT100-style escape sequences as well as get the output to match what other shells emit.
• Implementation of the lastpipe option.
• Initial partial implementation of the mapfile built-in, required by some completion helper functions. The most notable constraint is that we only support \n as a delimiter. There are other limitations as well, identified by calls to error::unimp() in the code.
• Stub implementation of bind built-in, emitting just enough to let some completion helper functions pass. Clearly more work is required here, as well as some thought as to which functions we can/should expose.
• Workarounds or fixes for various compat issues found with pattern matching, regex processing, and extended tests expressions.

Copilot reviewed 35 out of 35 changed files in this pull request and generated no suggestions.

[github-actions]

Test Results

    2 files      9 suites   1m 17s ⏱️
  553 tests   553 ✅ 0 💤 0 ❌
1 092 runs  1 092 ✅ 0 💤 0 ❌

Results for commit 7f0351b.

♻️ This comment has been updated with latest results.

[github-actions]

Performance Benchmark Report

Benchmark name	Baseline (μs)	Test/PR (μs)	Delta (μs)	Delta %
expand_one_string	3.44 μs	3.50 μs	0.06 μs	⚪ Unchanged
instantiate_shell	60.91 μs	62.51 μs	1.60 μs	🟠 +2.63%
instantiate_shell_with_init_scripts	31122.34 μs	30617.10 μs	-505.24 μs	⚪ Unchanged
parse_bash_completion	2889.09 μs	2838.09 μs	-51.00 μs	⚪ Unchanged
parse_sample_script	4.41 μs	4.37 μs	-0.04 μs	🟢 -0.98%
run_echo_builtin_command	90.80 μs	92.49 μs	1.69 μs	⚪ Unchanged
run_one_builtin_command	108.72 μs	110.91 μs	2.19 μs	⚪ Unchanged
run_one_external_command	1936.81 μs	1976.33 μs	39.52 μs	🟠 +2.04%
run_one_external_command_directly	1008.97 μs	1013.85 μs	4.88 μs	⚪ Unchanged

Code Coverage Report: Only Changed Files listed

Package	Base Coverage	New Coverage	Difference
brush-core/src/builtins/complete.rs	🔴 21.83%	🟠 56.43%	🟢 34.6%
brush-core/src/builtins/factory.rs	🟢 82.35%	🟢 82.5%	🟢 0.15%
brush-core/src/builtins/mapfile.rs	🔴 0%	🟢 76.6%	🟢 76.6%
brush-core/src/builtins/set.rs	🟠 70.18%	🟠 56.07%	🔴 -14.11%
brush-core/src/commands.rs	🟢 86.43%	🟢 86.83%	🟢 0.4%
brush-core/src/completion.rs	🔴 20.4%	🔴 28.42%	🟢 8.02%
brush-core/src/escape.rs	🟢 87.18%	🟢 87%	🔴 -0.18%
brush-core/src/expansion.rs	🟢 96.26%	🟢 96.21%	🔴 -0.05%
brush-core/src/extendedtests.rs	🟠 69.51%	🟠 70.3%	🟢 0.79%
brush-core/src/interp.rs	🟢 91.2%	🟢 91.23%	🟢 0.03%
brush-core/src/namedoptions.rs	🟠 53.85%	🟠 54.81%	🟢 0.96%
brush-core/src/options.rs	🟢 89.58%	🟢 89.8%	🟢 0.22%
brush-core/src/shell.rs	🟢 79.06%	🟢 77.99%	🔴 -1.07%
brush-core/src/sys/unix/terminal.rs	🔴 37.74%	🔴 32.65%	🔴 -5.09%
brush-interactive/src/basic/basic_shell.rs	🟢 100%	🟠 73.08%	🔴 -26.92%
brush-interactive/src/basic/raw_mode.rs	🔴 0%	🟢 94.12%	🟢 94.12%
brush-interactive/src/basic/term_line_reader.rs	🔴 0%	🔴 28.79%	🟢 28.79%
brush-parser/src/parser.rs	🟢 99.14%	🟢 99.15%	🟢 0.01%
brush-parser/src/tokenizer.rs	🟢 96%	🟢 96.03%	🟢 0.03%
brush-shell/src/events.rs	🔴 38.04%	🔴 37.23%	🔴 -0.81%
brush-shell/src/main.rs	🟢 90.91%	🟢 90.38%	🔴 -0.53%
brush-shell/src/shell_factory.rs	🔴 48.48%	🔴 34.78%	🔴 -13.7%
Overall Coverage	🟢 74.65%	🟢 74.29%	🔴 -0.36%

Minimum allowed coverage is 70%, this run produced 74.29%``76.79%

Copilot reviewed 38 out of 38 changed files in this pull request and generated no suggestions.