Add Process.WaitForExit(TimeSpan) polyfill (NET 7.0)

[Copilot]

Process.WaitForExit(TimeSpan timeout) was introduced in .NET 7.0 and is not available on older TFMs. This adds a polyfill so it can be used on .NET Framework, .NET Standard, and pre-7.0 .NET Core targets.

Changes

• PolyShim/Net70/Process.cs — Extension method polyfill for Process.WaitForExit(TimeSpan), guarded by FEATURE_PROCESS and !NET7_0_OR_GREATER. Validates the TimeSpan is within the [-1, int.MaxValue] ms range (matching the native API contract), then delegates to WaitForExit(int).
• PolyShim.Tests/Net70/ProcessTests.cs — Two tests covering the success (process exits within timeout) and timeout-elapsed (returns false) paths.

using var process = Process.Start("my-tool");

// Now usable on all supported TFMs
bool exited = process.WaitForExit(TimeSpan.FromSeconds(30));

[codecov]

Codecov Report

❌ Patch coverage is 94.44444% with 2 lines in your changes missing coverage. Please review.
✅ Project coverage is 90.81%. Comparing base (950c84c) to head (39cdcdc).
⚠️ Report is 1 commits behind head on prime.

Files with missing lines	Patch %	Lines
PolyShim/Net70/Process.cs	50.00%	1 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##            prime     #119      +/-   ##
==========================================
+ Coverage   90.75%   90.81%   +0.06%     
==========================================
  Files         282      284       +2     
  Lines        4898     4934      +36     
  Branches      401      404       +3     
==========================================
+ Hits         4445     4481      +36     
+ Misses        364      363       -1     
- Partials       89       90       +1     

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[Copilot]

Pull request overview

Adds a PolyShim polyfill for System.Diagnostics.Process.WaitForExit(TimeSpan) (introduced in .NET 7) so callers can use the TimeSpan overload on older target frameworks, along with tests and signature documentation updates.

Changes:

• Add Process.WaitForExit(TimeSpan) polyfill (guarded by FEATURE_PROCESS and !NET7_0_OR_GREATER) delegating to WaitForExit(int).
• Add Net70 tests intended to cover “exits within timeout” and “timeout elapsed” behaviors.
• Update Signatures.md to include the new member and adjust totals.

Reviewed changes

Copilot reviewed 3 out of 3 changed files in this pull request and generated 5 comments.

File	Description
Signatures.md	Documents the added Process.WaitForExit(TimeSpan) member and updates counts.
PolyShim/Net70/Process.cs	Implements the WaitForExit(TimeSpan) polyfill for pre-.NET 7 TFMs.
PolyShim.Tests/Net70/ProcessTests.cs	Adds tests for the new TimeSpan overload behavior.

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