Keep required CI and CodeQL checks green while skipping heavy work for Markdown-only pull requests

[Copilot]

Summary

This PR now keeps required checks running (and passing) on every pull request, including docs-only PRs.

Instead of skipping entire workflows at the trigger level, CI and CodeQL now:

• always run on pull requests, and
• detect whether the PR changes only Markdown files via the GitHub PR files API (actions/github-script),
• then skip expensive steps (lint/build/tests/analysis) only for Markdown-only PRs.

This preserves merge-required check behavior while still reducing unnecessary work for docs-only changes.

Original Prompt

Issue title: Skip CI checks when only Markdown files have changed

Issue description:
When the only changes are in Markdown files, most GitHub actions don't need to do anything. Only the ones that specifically deal with Markdown need to execute.

Skip steps like running unit tests when none of the files that would be tested have changed.

Manual acceptance tests

• A pull request that changes only Markdown files still shows successful CI Checks and CodeQL required checks (not skipped).
• A pull request that changes only Markdown files does not execute heavy CI steps (lint, unit tests, black-box tests, type tests).
• A pull request that changes only Markdown files does not execute CodeQL initialization/autobuild/analysis steps.
• A pull request that changes both Markdown and TypeScript files executes full CI and CodeQL step paths.
• Existing non-PR triggers (for example, CodeQL scheduled runs) continue to behave unchanged.

Tasks

• Reviewed workflow behavior against required-check merge constraints.
• Replaced trigger-level Markdown skipping with in-workflow docs-only detection in .github/workflows/ci.yaml.
• Replaced trigger-level Markdown skipping with in-workflow docs-only detection in .github/workflows/codeql.yml.
• Added conditional execution so heavy steps are bypassed only for docs-only PRs.
• Validated workflow updates and reran automated review/security validation.

[pmcelhaney]

The CI checks are required for merge. The actions should pass rather than skip.

[Copilot]

The CI checks are required for merge. The actions should pass rather than skip.

Updated so required checks no longer get skipped at the workflow trigger level. CI and CodeQL now always run on PRs, detect docs-only changes, and short-circuit heavy steps while returning successful required checks. Addressed in commit 1079b1d.