feat: add Sliding window function

[rjNemo]

Summary

• Add Sliding: creates sliding window views of a slice with specified window size

Implementation

• sliding.go: Sliding implementation with pre-allocation
• Returns independent window copies (non-mutating)
• Handles edge cases: empty, size <= 0, size > length, size == length
• Comprehensive tests
• Benchmark included

Testing

go test -v -run TestSliding
go test -bench=BenchmarkSliding -benchmem

All tests pass.

Examples

Sliding([]int{1,2,3,4,5}, 3)      // [[1,2,3], [2,3,4], [3,4,5]]
Sliding([]int{1,2,3,4}, 2)        // [[1,2], [2,3], [3,4]]
Sliding([]int{1,2,3}, 1)          // [[1], [2], [3]]
Sliding([]int{1,2,3}, 3)          // [[1,2,3]]
Sliding([]int{1,2,3}, 5)          // []

Use Cases

• Moving averages in time series data
• N-gram generation in text processing
• Pattern matching across sequences
• Rolling window computations

Related

Resolves Issue 19 from ACTION_PLAN.md

🤖 Generated with Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.67%. Comparing base (d622c8c) to head (e03ba5d).
⚠️ Report is 10 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #47      +/-   ##
==========================================
+ Coverage   98.63%   98.67%   +0.03%     
==========================================
  Files          39       40       +1     
  Lines         367      377      +10     
==========================================
+ Hits          362      372      +10     
  Misses          4        4              
  Partials        1        1              

Flag	Coverage Δ
unittests	98.67% <100.00%> (+0.03%)	⬆️

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