Refactor: Replace ArrayPool<T>.RentOwner extension with SpanPool<T>.Rent

[Copilot]

ISpanOwner<T> and its renting logic were awkwardly bolted onto ArrayPool<T> via an extension method. This promotes them to a first-class SpanPool<T> type with a cleaner, purpose-built API.

Changes

• New PowerKit/SpanPool.cs — introduces SpanPool<T> with a Shared static property (backed by ArrayPool<T>.Shared) and a Rent(int minimumLength = 1) method returning ISpanOwner<T>; ISpanOwner<T> and the private ArrayPoolSpanOwner<T> impl move here from the old extensions file
• Removed ArrayPoolExtensions.cs — extension(ArrayPool<T>) block with RentOwner is gone
• Updated FileExtensions.cs — single call site updated accordingly
• Tests — ArrayPoolExtensionsTests.cs replaced by SpanPoolTests.cs at the root test level

// Before
using var buffer = ArrayPool<byte>.Shared.RentOwner(bytes.Length * 2);

// After
using var buffer = SpanPool<byte>.Shared.Rent(bytes.Length * 2);

[Tyrrrz]

Retain the coding style from the removed test file @copilot

[Copilot]

Fixed in 00435dd. Each test now has a var pool = SpanPool<byte>.Shared; in its // Arrange section, matching the original style.

[Copilot]

Pull request overview

This PR refactors the temporary-span renting API by replacing the ArrayPool<T>.RentOwner() extension with a dedicated SpanPool<T> type, making the pooling abstraction a first-class concept in PowerKit.

Changes:

• Added SpanPool<T> (backed by ArrayPool<T>) and moved ISpanOwner<T> + implementation into the new file.
• Removed the ArrayPool<T>.RentOwner() extension and updated the only in-repo call site.
• Replaced the old extension-focused tests with SpanPool-focused tests.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
PowerKit/SpanPool.cs	Introduces SpanPool<T> + ISpanOwner<T> and the pooled-span owner implementation.
PowerKit/Extensions/FileExtensions.cs	Updates buffer renting in File.Contains() to use SpanPool<T>.Shared.Rent(...).
PowerKit/Extensions/ArrayPoolExtensions.cs	Removes the old RentOwner extension implementation.
PowerKit.Tests/SpanPoolTests.cs	Adds tests for renting and disposal behavior via SpanPool<T>.
PowerKit.Tests/Extensions/ArrayPoolExtensionsTests.cs	Removes tests for the deleted RentOwner extension.

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[Copilot]

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[codecov]

Codecov Report

❌ Patch coverage is 86.66667% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 93.88%. Comparing base (d826090) to head (e128826).
⚠️ Report is 2 commits behind head on prime.

Files with missing lines	Patch %	Lines
PowerKit/SpanPool.cs	80.00%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##            prime      #74   +/-   ##
=======================================
  Coverage   93.88%   93.88%           
=======================================
  Files         128      128           
  Lines        2534     2536    +2     
  Branches      201      201           
=======================================
+ Hits         2379     2381    +2     
  Misses        112      112           
  Partials       43       43           

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