fix(ci): Update e2e tests to import from ai instead of vertexai

[hsubox76]

Need to update the import statement in the E2E test after removing the firebase/vertexai alias in #9081

Also added some tsconfig fixes so that VSCode will not show false positive errors based on using @types/mocha (from the outer node_modules directory) for "describe" blocks instead of @types/jest.

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Latest commit: 146be5a

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[google-oss-bot]

Size Report ¹

Affected Products

No changes between base commit (5200f7b) and merge commit (dba2908).

Test Logs

• Base (5200f7b): https://github.com/firebase/firebase-js-sdk/actions/runs/16277687118
• Merge (dba2908): https://github.com/firebase/firebase-js-sdk/actions/runs/16280274687

1. https://storage.googleapis.com/firebase-sdk-metric-reports/5oecSDmOYe.html

[google-oss-bot]

Size Analysis Report ¹

Affected Products

No changes between base commit (5200f7b) and merge commit (dba2908).

Test Logs

• Base (5200f7b): https://github.com/firebase/firebase-js-sdk/actions/runs/16277687118
• Merge (dba2908): https://github.com/firebase/firebase-js-sdk/actions/runs/16280274687

1. https://storage.googleapis.com/firebase-sdk-metric-reports/H7cxBOl3pg.html