Fix CI: exclude demo/visual specs, fix oil-card→oil-chip selectors

- Grep pattern now matches full filenames (demo-walkthrough, visual-check)
- Updated all test files to use .oil-chip (new OilReference class name)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

frontend/cypress/e2e/performance.cy.js

@@ -38,7 +38,7 @@ describe('Performance', () => {
   it('oil reference page loads within 3 seconds', () => {
     const start = Date.now()
     cy.visit('/oils')
-    cy.get('.oil-card', { timeout: 3000 }).should('have.length.gte', 1)
+    cy.get('.oil-chip', { timeout: 3000 }).should('have.length.gte', 1)
     cy.then(() => {
       expect(Date.now() - start).to.be.lt(3000)
     })