feat: add Vitest test suite with store and utility tests

[Nic-dorman]

Summary

Set up Vitest with @nuxt/test-utils for unit and integration testing. Includes mock infrastructure and initial test coverage for the most critical frontend logic.

What's included

File	Purpose
vitest.config.ts	Nuxt test environment with happy-dom
tests/mocks/tauri.ts	Mock for @tauri-apps/api/core invoke() — lets tests simulate Tauri command responses
tests/mocks/appkit.ts	Mocks for WalletConnect/AppKit/wagmi (CommonJS modules that break in ESM test env)
tests/stores/settings.test.ts	Config load/save, devnet manifest detection, Sepolia detection
tests/stores/nodes.test.ts	Daemon connection flow, SSE event handling, status getters
tests/utils/wallet-config.test.ts	Chain ID selection, token/vault address overrides per network mode

Test coverage

19 tests across 3 suites:

• Settings store (6 tests): loads config from backend, handles corrupt config gracefully, activates devnet mode from manifest, detects Sepolia from RPC URL, stays in production mode without manifest, persists config changes
• Nodes store (6 tests): connects to daemon on startup, updates daemon URL on port change, sets disconnected when daemon unavailable, handles SSE node events, handles crash events, counts nodes by status
• Wallet config (7 tests): returns correct chain ID for mainnet/Sepolia/Anvil, returns correct token and vault addresses with devnet overrides

How to run

npm test          # watch mode
npm run test:run  # single run

Test plan

• All 19 tests pass locally
• Tauri invoke mock correctly intercepts all store commands
• AppKit/WalletConnect mocked to avoid CommonJS import errors

🤖 Generated with Claude Code