docs: restructure contributing docs and improve E2E test infrastructure

Move developer resources (setup, building, testing, code quality) into
CONTRIBUTING.md and refocus the website's contributing page on project
governance (roles, voting, CLA). Slim down localgit/README.md to a
summary now that CONTRIBUTING.md covers E2E setup in detail.

Rename E2E test repositories from real project names to clearly fake
names (test-owner/test-repo, e2e-org/sample-repo). Add fail-fast
pre-flight checks in E2E setup to detect missing Docker infrastructure.
Add Docker Hub login to CI workflow to avoid pull rate limits. Remove
outdated Mocha/Chai testing page from docs site and fix plugin import
paths.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: coopernetes

.github/workflows/e2e.yml

@@ -19,6 +19,16 @@ jobs:
       - name: Checkout code
         uses: actions/checkout@34e114876b0b11c390a56381ad16ebd13914f8d5 # v4
 
+      # Authenticate to Docker Hub to avoid pull rate limits.
+      # Skipped on fork PRs where secrets are unavailable — those runs
+      # fall back to unauthenticated pulls and may be rate-limited.
+      - name: Log in to Docker Hub
+        if: secrets.DOCKER_PASSWORD != ''
+        uses: docker/login-action@c94ce9fb468520275223c153574b00df6fe4bcc9 # v3
+        with:
+          username: finos
+          password: ${{ secrets.DOCKER_PASSWORD }}
+
       - name: Set up Docker Buildx
         uses: docker/setup-buildx-action@7c525be6cc8a882d5163ce04293cac18617c709f
 
@@ -47,6 +57,7 @@ jobs:
         run: |
           timeout 60 bash -c '
             while [ "$(docker compose ps | grep -c "Up")" -ne 3 ]; do
+              echo "Waiting for services to be ready..."
               sleep 2
             done
           ' || { echo "Service readiness check failed:"; docker compose ps; exit 1; }