Add CommandOptions with a working directory for the spawned process

[matt-edmondson]

Fixes #39.

Problem

ProcessStartInfo.WorkingDirectory was never assigned, so every command inherited the host process's current directory. The workarounds available to callers were a tool-specific flag where one exists (git -C), mutating the process-global Environment.CurrentDirectory (not thread-safe, races with concurrent calls), or shelling out through cmd /c cd && ... (reintroduces the quoting problems the argument-vector overloads exist to avoid).

Approach

Rather than add a parameter to every overload — and again for environment variables in #40 — this introduces a CommandOptions record to carry process-shaping settings:

public sealed record CommandOptions
{
	public AbsoluteDirectoryPath? WorkingDirectory { get; init; }
	public Elevation Elevation { get; init; } = Elevation.Default;
}

Three new overloads on the argument-vector shape accept it. All fourteen existing overloads keep their signatures and delegate through it, so no existing call changes behaviour and future options cost no new overloads.

WorkingDirectory is an AbsoluteDirectoryPath rather than a string on purpose: a relative directory would have to be resolved against the caller's current directory, which is exactly the process-global state this option exists to stop callers depending on. Making it absolute renders that ambiguity unrepresentable rather than merely discouraged.

Dependency note

This adds ktsu.Semantics.Paths and ktsu.Semantics.Strings, matching how AppDataStorage, SingleAppInstance and Schema consume them (the SDK's KTSU0006 analyzer requires the Strings reference be explicit, since WeakString is declared there).

Worth being deliberate about the cost: on net5.0–net7.0 and netstandard2.0/2.1 this pulls System.Text.Json, System.IO.Pipelines and System.Text.Encodings.Web in transitively, and those packages emit "doesn't support net5.0/6.0/7.0" build warnings — 10 of them, against a previously warning-free build. They are MSBuild warnings from targets files, not compiler warnings, so TreatWarningsAsErrors does not escalate them and the build stays green. The affected TFMs are all out of support, and netstandard2.1 already covers those consumers.

Testing

• ExecuteAsyncShouldStartTheProcessInTheGivenWorkingDirectory — runs cmd /c cd / pwd in a per-test temp directory and compares the reported leaf (leaf rather than full path, so a symlinked temp directory as on macOS doesn't produce a spurious failure).
• ExecuteAsyncShouldInheritTheCurrentDirectoryWhenNoWorkingDirectoryIsGiven — pins that an unset working directory leaves the previous behaviour untouched.
• ExecuteAsyncShouldThrowArgumentNullExceptionWhenOptionsAreNull.

Full suite: 27 passed, 2 skipped (elevated tests self-skip to avoid a UAC prompt). Builds clean across all eight target frameworks.

🤖 Generated with Claude Code

https://claude.ai/code/session_01LwKTWcmxe5mh6DsLRj5NGQ

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
88.9% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud