test: #144 add benchmark tests for fileManager module

[konard]

Summary

Implements benchmark tests for the FileManager module to measure and improve its performance as requested in issue #144.

Key areas benchmarked:

• File scanning operations: Both recursive (ScanFilesRecursively) and non-recursive (ScanFilesCurrentLevel) scanning with various directory sizes and depths
• File filtering operations: Size filters, extension filters, exclude patterns, date filters, and combined filter scenarios
• File size calculations: CalculateDirSize with concurrent processing in different directory structures
• Concurrent file operations: WalkFilesWithFilter performance with different file counts

Benchmark tests created:

Benchmark	Description
BenchmarkFileScanner_ScanFilesRecursively	Measures recursive file scanning with various file counts (10-500 files)
BenchmarkFileScanner_ScanFilesRecursively_Deep	Tests deeply nested directory structures (5-20 levels)
BenchmarkFileScanner_ScanFilesCurrentLevel	Measures current directory scanning performance
BenchmarkFileScanner_ScanEmptySubFolders	Tests empty folder detection performance
BenchmarkFileFilter_MatchesFilters	Measures filter matching with various filter types
BenchmarkFileFilter_ExcludeFilter	Tests exclude pattern matching with 0-10 patterns
BenchmarkCalculateDirSize	Measures directory size calculation performance
BenchmarkCalculateDirSize_Deep	Tests size calculation in deeply nested structures
BenchmarkWalkFilesWithFilter	Measures concurrent file walking performance
BenchmarkIsEmptyDir	Tests empty directory check performance
BenchmarkExpandTilde	Measures tilde expansion performance

Benchmark results summary:

All benchmarks measure:

• Operation time (ns/op)
• Memory allocations (B/op)
• Number of allocations (allocs/op)

Sample results from local run:

BenchmarkFileScanner_ScanFilesRecursively/Small_10files_2dirs    190167 ns/op    16083 B/op    190 allocs/op
BenchmarkFileScanner_ScanFilesRecursively/Large_500files_20dirs  1194499 ns/op   84556 B/op    1042 allocs/op
BenchmarkFileFilter_MatchesFilters/NoFilters                     7.232 ns/op     0 B/op        0 allocs/op
BenchmarkCalculateDirSize/Small_10files_2dirs                    169394 ns/op    13633 B/op    162 allocs/op

Test location:

internal/tests/benchmark/filemanager/filemanager_benchmark_test.go

How to run:

go test -bench=. -benchmem ./internal/tests/benchmark/filemanager/...

Test plan

• All benchmark tests pass locally
• Existing unit tests still pass
• Code follows gofmt formatting
• Benchmarks cover all key FileManager operations

Fixes #144

🤖 Generated with Claude Code

[konard]

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