[Foundation] FT-4: Make ParameterService instance-based and re-parseable

[ChrisonSimtian]

Summary

Make ParameterService instance-based and re-parseable, decoupled from the module-frozen argument source. Enables engine unit tests and reentrancy (re-running with different args in one process).

Findings (file:line)

• EnvironmentInfo.Arguments.cs:11 — internal static ArgumentParser ArgumentParser = new(Environment.GetCommandLineArgs().Skip(1)); captured once at module load, never refreshed.
• ParameterService.Statics.cs:11 — internal static ParameterService Instance = new(…) bound to that frozen parser → a second run can't override CLI parameters.

Scope

• Allow constructing ParameterService with an explicit args/env source.
• Hold the instance on BuildContext (FT-2); keep a static facade delegating to BuildContext.Current.Parameters for compatibility.

Acceptance criteria

• The engine can run with an injected args/env source — no dependency on Environment.GetCommandLineArgs() in tests.
• Existing parameter-injection behavior unchanged for normal CLI runs.

Notes

• Non-breaking (internal plumbing; static facade preserved).
• Depends on: FT-2.
• Size: M.