Set up WebDriver-based testing for the Tauri app with two tiers:
- Vitest browser-mode tests (*.tauri.test.ts) running inside the Tauri WebView
for plugin IPC testing (libsql, smoke tests)
- WDIO E2E tests (*.e2e.ts) for UI-level interaction testing
Key changes:
- Add webdriver Cargo feature gating tauri-plugin-webdriver
- Add runtime capability for remote URLs (webdriver builds only)
- Add vitest.tauri.config.mts and wdio.conf.ts connecting to embedded
WebDriver server on port 4445
- Add shared tauri-invoke helper for IPC from Vitest iframe context
- Add testing documentation in docs/testing.md
