feat: add TakeWhile and DropWhile functions

[rjNemo]

Summary

• Add TakeWhile: returns elements from the beginning while predicate is true
• Add DropWhile: drops elements from the beginning while predicate is true

Implementation

• takewhile.go: TakeWhile implementation with proper memory allocation
• dropwhile.go: DropWhile implementation with proper memory allocation
• Comprehensive tests for both functions including edge cases (empty, none match, all match, single element)
• Benchmarks included for performance validation

Testing

go test -v -run "TestTakeWhile|TestDropWhile"
go test -bench="BenchmarkTakeWhile|BenchmarkDropWhile" -benchmem

All tests pass.

Examples

nums := []int{1, 2, 3, 4, 5, 6}
TakeWhile(nums, func(n int) bool { return n < 4 }) // [1, 2, 3]
DropWhile(nums, func(n int) bool { return n < 4 }) // [4, 5, 6]

Related

Resolves Issue 14 from ACTION_PLAN.md

🤖 Generated with Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 98.69%. Comparing base (d622c8c) to head (482b899).
⚠️ Report is 4 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #42      +/-   ##
==========================================
+ Coverage   98.63%   98.69%   +0.05%     
==========================================
  Files          39       41       +2     
  Lines         367      383      +16     
==========================================
+ Hits          362      378      +16     
  Misses          4        4              
  Partials        1        1              

Flag	Coverage Δ
unittests	98.69% <100.00%> (+0.05%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.