Allow conditional trigger filtering without failing workflow runs

[MattSkala]

Problem

Our GitHub Actions workflow is triggered on the issues: [opened] event. Inside the workflow, we use a custom step to filter events so that only issues of type Bug are processed.

Following the Custom Trigger Filtering guide, the step exits with code 1 when the issue type does not match. While this correctly prevents the agent from running, it causes the entire workflow run to be marked as failed.

This leads to two side effects:

• The Actions tab becomes cluttered with red X runs that are not actual failures.
• It triggers the Workflow Failure issue mechanism, creating unnecessary noise.

Expected behavior

There should be a way to skip agent execution for non-matching events without marking the workflow as failed.

Ideally, the workflow run should be marked as skipped when the event does not match the filter.

Suggested improvement

Provide an alternative mechanism for conditional trigger filtering that allows workflows to exit early without returning a failure status, while still preventing agent execution.

[pelikhan]

@copilot fix the custom trigger filtering docs. Calling exit is not recommended.

Instead of using steps that can fail, the user can register a job and expose an output variable, then use that variable if the "if" command. The compiler will add the job as "needs" to activation + if and gracefully cancel.

Also suggest skip-if-match, skip-if-no-match.