Fix AbortSignal.timeout() jsdom compatibility and mock isolation in circuit breaker tests

[Copilot]

Two test infrastructure issues identified in PR #292 review:

1. AbortSignal.timeout() is undefined in Vitest's jsdom environment, causing runtime errors in fetchEzygoData()
2. Circuit breaker mock in health endpoint test was set before vi.resetModules(), so the fresh route import saw unmocked instance

Changes

• src/lib/ezygo-batch-fetcher.ts: Added createTimeoutSignal() helper with fallback to AbortController + setTimeout for environments without native AbortSignal.timeout()

function createTimeoutSignal(timeoutMs: number): AbortSignal {
  if (typeof AbortSignal !== 'undefined' && 'timeout' in AbortSignal) {
    return AbortSignal.timeout(timeoutMs);
  }
  const controller = new AbortController();
  setTimeout(() => controller.abort(), timeoutMs);
  return controller.signal;
}

• src/app/api/health/ezygo/__tests__/route.test.ts: Re-import circuit breaker after each vi.resetModules() to ensure mock applies to the route's module instance

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[Copilot]

Pull request overview

This PR fixes two test infrastructure issues discovered during the review of PR #292:

1. AbortSignal.timeout() is undefined in Vitest's jsdom environment, causing runtime errors when executing fetchEzygoData()
2. Circuit breaker mocks were set before vi.resetModules(), causing the freshly imported route module to see unmocked instances

Changes:

• Added createTimeoutSignal() helper function with environment detection and fallback support for jsdom
• Fixed mock isolation in circuit breaker tests by re-importing mocked modules after each vi.resetModules() call

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
src/lib/ezygo-batch-fetcher.ts	Added createTimeoutSignal() helper with AbortController + setTimeout fallback for environments lacking native AbortSignal.timeout() support
src/app/api/health/ezygo/__tests__/route.test.ts	Fixed mock isolation by re-importing circuit breaker module after vi.resetModules() to ensure mocks apply to fresh module instances

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