feat(playwright): Remove Cypress auth tests in favor of Playwright auth tests (#35938)

Co-authored-by: Claude <noreply@anthropic.com>

superset-frontend/playwright/tests/experimental/README.md

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+
+# Experimental Playwright Tests
+
+This directory contains Playwright tests that are still under development or validation.
+
+## Purpose
+
+Tests in this directory run in "shadow mode" with `continue-on-error: true` in CI:
+- Failures do NOT block PR merges
+- Allows tests to run in CI to validate stability before promotion
+- Provides visibility into test reliability over time
+
+## Promoting Tests to Stable
+
+Once a test has proven stable (no false positives/negatives over sufficient time):
+
+1. Move the test file out of `experimental/` to the appropriate feature directory:
+   ```bash
+   # From the repository root:
+   git mv superset-frontend/playwright/tests/experimental/dashboard/test.spec.ts \
+          superset-frontend/playwright/tests/dashboard/
+
+   # Or from the superset-frontend/ directory:
+   git mv playwright/tests/experimental/dashboard/test.spec.ts \
+          playwright/tests/dashboard/
+   ```
+
+2. The test will automatically become required for merge
+
+## Test Organization
+
+Organize tests by feature area:
+- `auth/` - Authentication and authorization tests
+- `dashboard/` - Dashboard functionality tests
+- `explore/` - Chart builder tests
+- `sqllab/` - SQL Lab tests
+- etc.
+
+## Running Tests
+
+```bash
+# Run all experimental tests (requires INCLUDE_EXPERIMENTAL env var)
+INCLUDE_EXPERIMENTAL=true npm run playwright:test -- experimental/
+
+# Run specific experimental test
+INCLUDE_EXPERIMENTAL=true npm run playwright:test -- experimental/dashboard/test.spec.ts
+
+# Run in UI mode for debugging
+INCLUDE_EXPERIMENTAL=true npm run playwright:ui -- experimental/
+```
+
+**Note**: The `INCLUDE_EXPERIMENTAL=true` environment variable is required because experimental tests are filtered out by default in `playwright.config.ts`. Without it, Playwright will report "No tests found".