Add Polysharp and adjustments that do not break legacy frameworks

[adamhathcock]

Fixes #1329

This pull request introduces significant changes to the mutability of various options and configuration classes across the codebase, shifting from immutable init-only properties to mutable set properties. This enables modifying options after object creation, increasing flexibility in how these objects are used and configured. Additionally, the PR updates documentation to reflect these changes and adds a new package dependency.

Key changes include:

Mutability Changes Across Options and Records:

• Changed most properties in options interfaces and records (such as IExtractionOptions, IReaderOptions, IWriterOptions, ExtractionOptions, ReaderOptions, GZipWriterOptions, SevenZipWriterOptions, and CompressionContext) from init-only to standard set properties, making them mutable after construction. This impacts how these objects can be used, allowing for property modifications post-instantiation. [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16]

• Refactored ArchiveInformation from a positional record with init-only properties to a class with mutable properties and an explicit constructor, improving clarity and consistency with the new mutability model.

Documentation and Usability Updates:

• Updated XML documentation and remarks in several files to clarify that options can now be configured with property setters, not just via constructors or with expressions, reflecting the move to mutable properties. [1] [2] [3]

Dependency Management:

• Added a new global package reference to PolySharp version 1.15.0 in Directory.Packages.props and updated the lock file accordingly. [1] [2]

[Copilot]

Pull request overview

This PR updates the repo’s dependency set/lock files to introduce PolySharp across projects and refreshes some pinned packages, aiming to improve cross-target compatibility (including .NET Framework 4.8 scenarios).

Changes:

• Added PolySharp 1.15.0 as a global package reference and updated corresponding packages.lock.json files.
• Updated Microsoft.NET.ILLink.Tasks to 10.0.7 in src/SharpCompress/packages.lock.json.
• Expanded the test lock file to include Windows RID-specific transitive dependencies.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
Directory.Packages.props	Adds PolySharp as a GlobalPackageReference to apply across the solution.
build/packages.lock.json	Locks build project dependencies including the new PolySharp direct dependency.
src/SharpCompress/packages.lock.json	Locks library dependencies; includes PolySharp and updates Microsoft.NET.ILLink.Tasks.
tests/SharpCompress.Performance/packages.lock.json	Locks performance test dependencies including PolySharp.
tests/SharpCompress.Test/packages.lock.json	Locks test dependencies including PolySharp and adds Windows RID-specific transitive deps.

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[adamhathcock]

@copilot ensure any thing else that is similar that would break net48 is accounted for and tested. Make a note in the AGENTS.md about things like this

[Copilot]

@copilot ensure any thing else that is similar that would break net48 is accounted for and tested. Make a note in the AGENTS.md about things like this

Handled in 9699907. I expanded the compatibility regression test to scan the exported API for init-only and required-member metadata, validated a temporary C# 7.3 net48 consumer build against the branch, and added an AGENTS.md note so future public API changes keep older-language consumers in mind.