Expose null progress reporter detection

[volksec]

Summary

• export isNullProgressReporter from vscode-languageserver
• let consumers distinguish a no-op work-done reporter without inspecting its constructor
• replace the server test's constructor.name check with the public helper
• cover both real and null work-done reporters

Motivation

Consumers currently need to rely on implementation details to determine whether a request supplied a real work-done reporter. For example, Pyright compared the reporter constructor with a reporter created by attachWorkDone. A public type guard makes this check explicit and keeps NullProgressReporter itself private.

This avoids adding a required property to WorkDoneProgressReporter, which would break external implementations of that interface.

Fixes #847.

Validation

• npm --prefix server run all
  • TypeScript compilation passed
  • ESLint passed
  • 13 tests passed
• git diff --check

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[volksec]

@microsoft-github-policy-service agree

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