chore: skip build and test steps for documentation-only changes

[AKnassa]

What this does

Stops documentation-only pull requests from running the entire build and test pipeline.

Why

Fix a typo in a markdown file today and CI still installs a Rust toolchain and wasm-pack, builds every package, downloads Playwright browsers, and runs the full end-to-end and validation suites — and ci-validate-platforms does all of that again across three operating systems.

That is slow for contributors and expensive for the project, and none of it can tell you anything about a markdown file.

What changed

Follows the implementation plan from the issue.

• ci-validate-pr.yml — a step after checkout works out whether the pull request touches any non-documentation file, and the expensive steps (toolchain install, build, browser install, unit tests, end-to-end tests, final validation) only run when it does. Change-file validation and linting still run every time, unconditionally.
• ci-validate-platforms.yml — documentation paths are excluded from the push and pull_request triggers. The scheduled and manual runs are untouched, so the full matrix still runs on its own cadence.
• azure-pipelines-ci.yml — documentation paths excluded from the PR trigger.

The detection fails open: anything it is unsure about is treated as source, so a real code change can never be mistaken for docs and skip its tests. Runs that are not pull requests always run the full pipeline.

One question for maintainers, please read

Are ci-validate-platforms or the Azure PR check configured as required status checks on main?

If they are, a skipped workflow never reports a status, and documentation-only PRs will sit forever on "Expected — waiting for status to be reported" — the exact opposite of the goal. Branch protection settings are not visible in the repository, so this cannot be checked from here.

If they are required, the fix is to keep the workflow running but make its jobs no-op, rather than skipping the workflow. Happy to change it to that shape — just say the word.

How to see it

The detection logic is a small script with its own unit tests (build/test/, 27 tests, wired into lage test:node), covering documentation-only changes, source changes, mixed changes, renames, deletions, and paths with spaces.

Beyond that: open a doc-only PR on a fork and watch the build and test steps report as skipped while lint and change-file validation still run green; then open a mixed docs-and-source PR and watch the full pipeline run.

Fixes #7339

[azure-pipelines]

Azure Pipelines:
There may be pipelines that require an authorized user to comment /azp run to run.

[azure-pipelines]

Azure Pipelines:
There may be pipelines that require an authorized user to comment /azp run to run.