feat(interp): add shell globbing benchmarks

[AlexandreYang]

Summary

• Add 11 benchmarks covering shell glob expansion scenarios: star, prefix, suffix, question mark, bracket, nested, no-match, multiple patterns, for-loop iteration, and small/large directories
• Add 3 memory-bounded assertion tests (TestGlob*MemoryBounded) that verify glob expansion stays within allocation ceilings
• Goal: establish baselines to spot improvements, regressions, or places where tighter limits are needed

Benchmarks

Benchmark	Scenario
BenchmarkGlobStar	echo * in 1000-entry dir
BenchmarkGlobStarLargeDir	echo * in 10000-entry dir
BenchmarkGlobPrefix	echo file0* in 1000-entry dir
BenchmarkGlobSuffix	echo *.txt in 1000-entry dir
BenchmarkGlobQuestionMark	echo file????.txt in 1000-entry dir
BenchmarkGlobBracket	echo file[0-4]*.txt in 1000-entry dir
BenchmarkGlobNested	echo */* across 20 dirs × 50 files
BenchmarkGlobNoMatch	echo *.xyz (no matches)
BenchmarkGlobMultiplePatterns	4 glob patterns in one command
BenchmarkGlobForLoop	for f in *.txt; do :; done
BenchmarkGlobSmallDir	echo * in 10-entry dir (baseline)

Test plan

• go test ./interp/ -run "TestGlob.*MemoryBounded" passes
• go test ./interp/ -bench "BenchmarkGlob" -benchmem runs successfully
• CI passes

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