docs(actions): clarify github.ref event semantics

[aniruddhaadak80]

Why:

Closes: #43055

The github.ref description is rendered inside the context reference table as one dense sentence that mixes event types and makes the pull request cases difficult to distinguish. The issue's reproduction shows that a merged pull_request run uses the base branch, while unmerged runs use the pull request merge ref. A previous clarification corrected one phrase, but did not separate the event-specific cases or make the ref formats explicit.

What's being changed (if available, include any code snippets, screenshots, or gifs):

• Rework the shared github.ref description into explicit push, unmerged and merged pull_request, pull_request_target, release, and fallback cases.
• State the fully formed branch, tag, and pull request merge ref formats alongside those cases.
• Keep the existing pull request merge-branch reference link.
• Evidence: issue The gihub.ref description is confusing and incorrect, particularly for PRs #43055 documents event-specific workflow runs and the current shared reusable reproduces the ambiguous wording.
• Testing:
  • npm run build - passed.
  • npm run lint-content -- --paths data/reusables/actions/ref-description.md content/actions/reference/workflows-and-actions/contexts.md - passed with no errors.
  • npm test -- src/content-render/tests/render-changed-and-deleted-files.ts - 2 tests passed.
  • git diff --check - passed.

Check off the following:

• A subject matter expert (SME) has reviewed the technical accuracy of the content in this PR. In most cases, the author can be the SME. Open source contributions may require an SME review from GitHub staff.
• The changes in this PR meet the docs fundamentals that are required for all content.
• All CI checks are passing and the changes look good in the review environment.

[github-actions]

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Table of review links

Note: Please update the URL for your staging server or codespace.

The table shows the files in the content directory that were changed in this pull request. This helps you review your changes on a staging server. Changes to the data directory are not included in this table.

Source	Review	Production	What Changed
actions/reference/workflows-and-actions/contexts.md	fpt ghec ghes@ 3.22 3.21 3.20 3.19 3.18 3.17	fpt ghec ghes@ 3.22 3.21 3.20 3.19 3.18 3.17	from reusable
actions/reference/workflows-and-actions/variables.md	fpt ghec ghes@ 3.22 3.21 3.20 3.19 3.18 3.17	fpt ghec ghes@ 3.22 3.21 3.20 3.19 3.18 3.17	from reusable

Key: fpt: Free, Pro, Team; ghec: GitHub Enterprise Cloud; ghes: GitHub Enterprise Server

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[subatoi]

I'm going to close this out—we haven't marked this as ready for community contributions yet, and are yet to make a determination about the best way to tackle the problem. Apologies that this won't be the outcome you were hoping for