[WC-3513] Enable react and update to Atlas 4

[leonardomendix]

Pull request type

Test related change (New E2E test, test automation, etc.)

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Description

This PR updates the used Mendix version to 11.15.0 and, through feature flags, enables React in the test projects and updates Atlas to version 4.

What should be covered while testing?

E2E tests should continue to pass in the automation.

[github-actions]

AI Code Review

⚠️ Approved with suggestions — low-severity items only, safe to merge

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What was reviewed

File	Change
automation/run-e2e/docker/mxbuild.Dockerfile	Added libgdiplus, libfontconfig1, and LD_PRELOAD env for font rendering
automation/run-e2e/docker/mxbuildRC.Dockerfile	Same font library additions as mxbuild.Dockerfile
automation/run-e2e/lib/ci.mjs	Flag renamed from --modern-client → --modern-web-client
automation/scripts/update-screenshots-local.mjs	Propagates --modern-web-client flag to local mxbuild command
packages/pluggableWidgets/*/package.json (9 packages)	e2e script bumped to MX 11.15.0 + MODERN_CLIENT=--modern-web-client; test project branches switched to Atlas 4 variants with atlasCoreVersion/atlasThemeTag
packages/pluggableWidgets/combobox-web/e2e/Combobox.spec.js	Scoped locator to .modal-body to avoid ambiguity after Atlas 4 DOM changes
packages/pluggableWidgets/gallery-web/e2e/GallerySelection.spec.js	Unchanged logic; diff is whitespace-only around isHidden() calls
Screenshot baselines (*.png across 9 widgets)	Updated to match Atlas 4 / React rendering

Skipped (out of scope): pnpm-lock.yaml, dist/

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Findings

⚠️ Low — e2edev scripts not updated for datagrid-web and tree-node-web

File: packages/pluggableWidgets/datagrid-web/package.json line 37
File: packages/pluggableWidgets/tree-node-web/package.json (e2edev line)
Note: The e2e scripts were bumped to MX 11.15.0 with MODERN_CLIENT, but the e2edev scripts still reference the old versions (10.24.12.86709 for datagrid, 11.12.0 for tree-node). Developers running pnpm run e2edev locally will use a different Mendix version than CI, which could mask regressions. Consider aligning them or adding a comment explaining the intentional divergence.

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⚠️ Low — GallerySelection.spec.js uses .isHidden() without await

File: packages/pluggableWidgets/gallery-web/e2e/GallerySelection.spec.js lines 12, 24
Note: page.locator(".mx-name-feedback1").isHidden() returns a Promise<boolean> that is not awaited and the result is not asserted. This means the visibility check is silently skipped. It was already there before this PR, but since the file was touched the PR is a good opportunity to fix it. Either:

await expect(page.locator(".mx-name-feedback1")).toBeHidden();

or remove the line if the check is intentionally passive.

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Positives

• Flag rename from --modern-client → --modern-web-client is applied consistently across both the Dockerfile ENV LD_PRELOAD path and the compose environment builder in ci.mjs, avoiding a partial migration.
• Font library dependencies (libgdiplus, libfontconfig1) added to both mxbuild.Dockerfile and mxbuildRC.Dockerfile symmetrically — no divergence between stable and RC build images.
• atlasCoreVersion and atlasThemeTag are now explicit in every updated package.json, making the Atlas version used for E2E tests auditable at a glance.
• Combobox locator scoped to .modal-body is a targeted fix that avoids over-specifying the selector.