fix: add PR context check to prevent undefined ref error

[aditigopalan]

Description

This PR fixes an issue in the JSON-LD conversion workflow where the action was failing with the error "Cannot read properties of undefined (reading 'ref')" when triggered manually or by a release event.

Changes

• Added a PR context check to conditionally run PR-related steps
• The workflow now only attempts to fetch and push PR changes when triggered by a pull request
• Manual triggers and release events will skip the PR-related steps while still performing the JSON-LD conversion

Testing

• Successfully tested the workflow with a manual trigger on this branch
• The JSON-LD conversion completes without errors
• PR-related steps are properly skipped when not in a PR context

Fixes #509

[Copilot]

Pull Request Overview

This PR fixes an error in the JSON-LD conversion workflow by adding a PR context check so that PR-specific steps are only executed when applicable.

• Introduces a condition to set and check the PR context.
• Conditionally executes the pr-fetch and pr-push steps.
• Prevents the workflow from attempting PR operations during manual or release events.

Comments suppressed due to low confidence (2)

.github/workflows/ci-lint-validate-convert.yml:89

• [nitpick] Consider renaming the step id 'check_pr' to a more descriptive identifier such as 'pr_context_check' to improve readability.

- name: Check if in PR context

.github/workflows/ci-lint-validate-convert.yml:109

• [nitpick] Ensure consistency in naming by using the same descriptive identifier for conditional steps across the workflow.

- name: Push changes