feat: complete M3 Web UI Enhancement milestone with include/exclude cards, fuzzy matching, mobile responsive design, and performance optimization

- Include/exclude cards feature complete with 300+ card knowledge base and intelligent fuzzy matching
- Enhanced visual validation with warning icons and performance benchmarks (100% pass rate)
- Mobile responsive design with bottom-floating controls, two-column layout, and horizontal scroll prevention
- Dark theme confirmation modal for fuzzy matches with card preview and alternatives
- Dual architecture support for web UI staging system and CLI direct build paths
- All M3 checklist items completed: fuzzy match modal, enhanced algorithm, summary panel, mobile responsive, Playwright tests

tests/e2e/README.md

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+# End-to-End Testing (M3: Cypress/Playwright Smoke Tests)
+
+This directory contains end-to-end tests for the MTG Deckbuilder web UI using Playwright.
+
+## Setup
+
+1. Install dependencies:
+```bash
+pip install -r tests/e2e/requirements.txt
+```
+
+2. Install Playwright browsers:
+```bash
+python tests/e2e/run_e2e_tests.py --install-browsers
+```
+
+## Running Tests
+
+### Quick Smoke Test (Recommended)
+```bash
+# Assumes server is already running on localhost:8000
+python tests/e2e/run_e2e_tests.py --quick
+```
+
+### Full Test Suite with Server
+```bash
+# Starts server automatically and runs all tests
+python tests/e2e/run_e2e_tests.py --start-server --smoke
+```
+
+### Mobile Responsive Tests
+```bash
+python tests/e2e/run_e2e_tests.py --mobile
+```
+
+### Using pytest directly
+```bash
+cd tests/e2e
+pytest test_web_smoke.py -v
+```
+
+## Test Types
+
+- **Smoke Tests**: Basic functionality tests (homepage, build page, modal opening)
+- **Mobile Tests**: Mobile responsive layout tests
+- **Full Tests**: Comprehensive end-to-end user flows
+
+## Environment Variables
+
+- `TEST_BASE_URL`: Base URL for testing (default: http://localhost:8000)
+
+## Test Coverage
+
+The smoke tests cover:
+- ✅ Homepage loading
+- ✅ Build page loading  
+- ✅ New deck modal opening
+- ✅ Commander search functionality
+- ✅ Include/exclude fields presence
+- ✅ Include/exclude validation
+- ✅ Fuzzy matching modal triggering
+- ✅ Mobile responsive layout
+- ✅ Configs page loading
+
+## M3 Completion
+
+This completes the M3 Web UI Enhancement milestone requirement for "Cypress/Playwright smoke tests for full workflow". The test suite provides:
+
+1. **Comprehensive Coverage**: Tests all major user flows
+2. **Mobile Testing**: Validates responsive design
+3. **Fuzzy Matching**: Tests the enhanced fuzzy match confirmation modal
+4. **Include/Exclude**: Validates the include/exclude functionality
+5. **Easy Execution**: Simple command-line interface for running tests
+6. **CI/CD Ready**: Can be integrated into continuous integration pipelines