ci: Migrates some GH workflows to reusable actions

[jvbriones]

Migrates some GH workflows to reusable actions.

follow-up PR of these:

• refactor!: Migrate remaining workflows to actions github-tools#169
• refactor!: Migrate remaining release-related workflows to actions github-tools#168

Description

Changelog

CHANGELOG entry:

Related issues

Fixes:

Manual testing steps

Feature: my feature name

  Scenario: user [verb for user action]
    Given [describe expected initial app state]

    When user [verb for user action]
    Then [describe expected outcome]

Screenshots/Recordings

Before

After

Pre-merge author checklist

• I’ve followed MetaMask Contributor Docs and MetaMask Mobile Coding Standards.
• I've completed the PR template to the best of my ability
• I’ve included tests if applicable
• I’ve documented my code using JSDoc format if applicable
• I’ve applied the right labels on the PR (see labeling guidelines). Not required for external contributors.

Pre-merge reviewer checklist

• I've manually tested the PR (e.g. pull and build branch, run the app, test code being changed).
• I confirm that this PR addresses all acceptance criteria described in the ticket it closes and includes the necessary testing evidence such as recordings and or screenshots.

---

Note

Migrates CI workflows from reusable workflows to explicit action steps and adds manual dispatch triggers where applicable.

• Workflows:
  • check-pr-max-lines.yml:
    • Replace reusable workflow with action MetaMask/github-tools/.github/actions/pr-line-check@v1.
    • Add runs-on: ubuntu-latest; configure max-lines and ignore-patterns.
  • flaky-test-report.yml:
    • Replace reusable workflow with action .../flaky-test-report@v1.
    • Add workflow_dispatch; set runs-on; pass repository, workflow-id, github-token, and Slack webhook.
  • post-merge-validation.yml:
    • Replace reusable workflow with action .../post-merge-validation@v1.
    • Add workflow_dispatch; set runs-on; pass repo, start-hour-utc, github-token, and GCP creds.

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[github-actions]

CLA Signature Action: All authors have signed the CLA. You may need to manually re-run the blocking PR check if it doesn't pass in a few minutes.

[Mrtenz]

Here as well.

Thanks for taking care of this by the way!

[github-actions]

🔍 Smart E2E Test Selection

• Selected E2E tags: None (no tests recommended)
• Risk Level: low
• AI Confidence: 90%

click to see 🤖 AI reasoning details

The changes in this PR are limited to three GitHub Actions workflow files that handle CI/CD infrastructure tasks:

1. check-pr-max-lines.yml: Refactored to use a GitHub action directly instead of a reusable workflow for checking PR line limits
2. flaky-test-report.yml: Refactored to use a GitHub action for generating flaky test reports, plus added manual trigger capability
3. post-merge-validation.yml: Refactored to use a GitHub action for post-merge validation tracking, plus added manual trigger capability

Why no E2E tests are needed:

• These are pure CI/CD infrastructure changes that don't modify any application code
• No changes to the E2E test framework, test execution, or test infrastructure itself
• No changes to app/core/, controllers, Engine, or any critical application paths
• The workflows being modified are for monitoring and validation purposes (PR checks, flaky test reporting, post-merge validation)
• The changes are refactoring how external actions are called (from reusable workflows to direct actions), maintaining the same functionality
• No impact on user-facing features or wallet functionality

Risk Assessment:

• Low risk: These are infrastructure-only changes
• The workflows themselves will validate their own functionality when they run
• If there are issues with the workflow syntax, they will be caught by GitHub Actions validation before any E2E tests would run
• The changes don't affect what tests run or how they execute, only how CI/CD jobs are structured

The confidence is high (90%) because the changes are clearly scoped to CI/CD infrastructure with no application code impact. Running E2E tests would not provide meaningful validation of these workflow configuration changes.

View GitHub Actions results

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud