E2E tests

[kashifpk]

Description

Create end-to-end tests for the UI.

Tasks

• Set up Playwright or Vitest for E2E
• Test basic conversation flow
• Test model selection
• Test tool call display
• Add CI workflow

Test Scenarios

• Send message and receive response
• Select different model
• View tool call details
• Handle connection errors

Acceptance Criteria

• E2E tests run in CI
• Basic user flows covered
• Tests use mock backend

[kashifpk]

Moved to Post-MVP phase - not blocking for initial release.