Add telemetry for --help, --version, and --info options

[marcpopMSFT]

Motivation

The CLI collects telemetry for command invocations, but --help, --version, and --info have a gap: root-level invocations like dotnet --help produce an empty verb, making them invisible in telemetry. Subcommand help like dotnet build --help emits telemetry with verb=build but is indistinguishable from an actual dotnet build execution. This PR closes both gaps.

Changes

Modifies TelemetryFilter.FilterImpl with two small additions:

1. Meaningful verb for root-level options -- When RootSubCommandResult() returns an empty string and the active action is a terminating option (--help, --version, --info), the option's name is used as the verb instead of empty string.

2. help=true property for help requests -- When parseResult.Action is a PrintHelpAction (covers both managed and AOT paths), a help=true property is added to the telemetry event. This distinguishes dotnet build --help from dotnet build.

Resulting telemetry

Command	verb (hashed)	help property
dotnet --help	--help	true
dotnet --version	--version	--
dotnet --info	--info	--
dotnet build --help	build	true
dotnet build	build	--

Performance

Benchmarked with 10-15 iterations per command. The telemetry infrastructure cost (~300ms for OpenTelemetry/TelemetryClient init) is pre-existing and unchanged. Our filter additions are just two type checks and one dictionary insert -- nanosecond-scale operations. TrackEvent dispatches via Task.Run() (fire-and-forget), so event emission does not block command execution.

Command	Built SDK (avg)	System SDK (avg)	Delta
--version	576ms	645ms	-70ms
--help	597ms	654ms	-58ms
build --help	615ms	584ms	+32ms (noise)

No measurable regression.

Testing

Added 5 new tests in TelemetryFilterTest.cs covering all new scenarios. All 12 telemetry filter tests pass.

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[baronfel]

Excellent, cross-cutting change 👍

[Copilot]

Pull request overview

This PR improves .NET CLI telemetry classification for terminating help/version/info flows by (1) ensuring root-level option invocations (e.g., dotnet --help) produce a non-empty verb and (2) adding a help=true property to distinguish dotnet <verb> --help from actual command executions.

Changes:

• Update TelemetryFilter.FilterImpl to synthesize a verb for terminating root-level option actions when no subcommand is present.
• Add a help=true telemetry property when the active action is PrintHelpAction (including the AOT-derived action).
• Add MSTest coverage for root --help/--version/--info and subcommand --help scenarios.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
src/Cli/dotnet/Telemetry/TelemetryFilter.cs	Adds logic to derive a telemetry verb for terminating root options and adds a help property for help actions.
test/dotnet.Tests/TelemetryTests/TelemetryFilterTest.cs	Adds tests covering the new verb behavior for root options and the new help property behavior for help requests.