Support no-op for PR pipeline

[raych1]

Description

• Adds a manual-run SkipPrValidation parameter to the PR pipeline.
• Passes the flag to the archetype SDK client template.
• Runs only a NoOp stage for manual PR validation runs when SkipPrValidation is true, leaving normal PR/CI behavior unchanged.

Validation

• Parsed changed YAML files with PyYAML.
• Ran eng/common/scripts/Verify-Resource-Ref.ps1.
• Ran git diff --check.

[Copilot]

Pull request overview

This PR adds an opt-in SkipPrValidation parameter to the Python PR pipeline so that a manually-queued run can short-circuit normal PR/CI validation and execute only a lightweight no-op stage. This is useful for forcing a pipeline run (e.g., to refresh required-check status) without paying the cost of full validation. Automatic, PR-triggered runs are unaffected because the skip is additionally gated on Build.Reason == 'Manual'.

Changes:

• Adds a SkipPrValidation boolean parameter (default false) to both pullrequest.yml and the archetype-sdk-client.yml template, threading it through.
• Conditionally inserts a NoOp stage (compile-time) and skips the Build stage (runtime condition) / release template (compile-time) when SkipPrValidation is true on a manual run.

Reviewed changes

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

File	Description
eng/pipelines/pullrequest.yml	Declares the new SkipPrValidation parameter and forwards it to the archetype template.
eng/pipelines/templates/stages/archetype-sdk-client.yml	Accepts SkipPrValidation, adds a NoOp stage, and gates the Build stage and release template on the skip condition.

Notes from review:

• I verified variables['Build.Reason'] is valid in compile-time ${{ if }} expressions here (widely used, e.g. check-spelling.yml:37, archetype-python-release.yml:356) and that the runtime eq(${{ parameters.<bool> }}, true) pattern has precedent (docindex.yml:122), so the change is functionally correct across the manual-skip, manual-normal, and PR-triggered cases.
• One non-blocking nit: the Build gate uses a runtime condition: while the NoOp and release gates use compile-time ${{ if }}; unifying them would fully omit Build (rather than showing it as skipped) and keep the three identical conditions consistent.