refactor: narrow nav.tsx API import to remove mock barrel dependency (#387)

[MarcusDavidG]

Summary

Fixes #387.

Problem

components/nav.tsx imported getApi from @/lib/api (the barrel). The barrel (lib/api/index.ts) re-exported resetMockData, applyMockScenario, replayMockEvent, etc. from mock-boundary, which in turn imported from the large lib/api/mock.ts aggregation module. This meant any syntax error in mock.ts could prevent the navigation component from compiling, even though the nav only needs getApi.

Solution

1. New lib/api/factory.ts — narrow module that exports only getApi (and the version helpers it already re-exported). Imports only what getApi strictly needs: config, LiveAccessApi, and createMockAccessApi from mock-boundary.

2. Updated components/nav.tsx — imports getApi from @/lib/api/factory instead of the full barrel. The nav's dependency graph no longer includes the mock-utility re-exports.

3. Updated lib/api/index.ts — the barrel now re-exports getApi from ./factory. All existing consumers of @/lib/api are unaffected — zero callsite changes needed outside nav.

Acceptance criteria checklist

• Every API import in components/nav.tsx is demonstrably used (getApi is called in the useQuery queryFn)
• The component does not depend on mock implementation details (resetMockData, applyMockScenario, etc. are no longer in its import graph)
• Dependency graph avoids unnecessary coupling to the large mock module
• Navigation behavior remains unchanged (same getApi factory, same runtime logic)
• No other consumers broken — all other files importing from @/lib/api continue to work via the barrel re-export