E2E Test Selection:
All 4 changed files are purely CI/build infrastructure:

1. .github/workflows/build.yml: Adds a new CI step to run check-env-whitespace.js after secrets are applied. This is a build pipeline validation step only.

2. scripts/build.sh: Adds defensive whitespace trimming in the remapEnvVariable function. This only affects how environment variables are set during the build process — no app code is changed.

3. scripts/check-env-whitespace.js: A new validation script that checks environment variables for leading/trailing whitespace. Runs at build time only, never shipped to the app.

4. scripts/set-secrets-from-config.js: Enhanced to trim whitespace from secret values before writing to GITHUB_ENV, with improved warning messages.

None of these changes affect:

• Any application source code or UI components
• Any controllers, Engine, or state management
• Any E2E test infrastructure (page objects, fixtures, test files)
• Any navigation, modals, confirmations, or user flows

These are purely defensive build-time improvements to prevent malformed secrets (with trailing newlines) from being baked into the JS bundle. The changes are semantically no-ops for well-formed secrets and only add protective validation. No E2E tests need to run to validate these changes, and there is no performance impact.

Performance Test Selection:
All changes are build-time CI scripts and workflow steps. No application code, rendering logic, state management, or user flows are affected. There is zero performance impact on the running app.