Automate removal of the ready-for-review label

[simongdavies]

What

Automates removal of the ready-for-review label from a pull request once it is
no longer awaiting review.

The label is removed when any of the following become true:

• the PR is closed or merged,
• the PR is converted to a draft,
• the PR has two or more approvals, or
• the PR has two or more change requests.

Adding the label stays a manual / author action (now documented in
docs/github-labels.md); only removal is automated.

How

The reusable engine lives in the organisation's .github repository
(hyperlight-dev/.github) so every repository can share one implementation.
This PR adds the hyperlight-side pieces:

• .github/workflows/ready-for-review-label.yml — a thin caller that
  triggers on pull_request_target (closed, converted_to_draft) and
  pull_request_review (submitted, dismissed) and invokes the shared
  engine, pinned to commit 12c76e8.
• docs/github-labels.md — a new "Review readiness" section describing when
  the label is added (manually) and removed (automatically).

pull_request_target is used so the job has a write-scoped token for pull
requests from forks. This is safe because the engine never checks out or
executes PR code — it only reads PR metadata and removes a label.

Notes

• Review counting uses the GraphQL latestOpinionatedReviews field, so only
  each reviewer's most recent approve / request-changes counts (comments are
  ignored and a reviewer is never double-counted).
• The approval and change-request thresholds are workflow inputs that default
  to 2.
• Validated locally: the workflow YAML passes schema checks and the engine's
  run script passes bash -n.

[Copilot]

Pull request overview

This PR introduces an automated mechanism to remove the ready-for-review label when a pull request is no longer awaiting review, by wiring repository events into a reusable org-wide workflow. It also documents the intended manual-add / automatic-remove behavior in the project’s label documentation.

Changes:

• Adds a new GitHub Actions workflow that calls the shared hyperlight-dev/.github “manage-ready-for-review” reusable workflow on relevant PR/review events.
• Documents the “ready-for-review” label lifecycle (when to add it, and when it will be removed automatically).

Reviewed changes

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

File	Description
.github/workflows/ready-for-review-label.yml	Adds the caller workflow that triggers on PR closure/draft conversion and review submission/dismissal, and invokes the pinned org-wide reusable workflow.
docs/github-labels.md	Documents the ready-for-review label purpose and the automatic removal criteria.