Fix storageState IndexedDB falsy primitive round-tripping

[fallintoplace]

Summary

• preserve falsy primitive IndexedDB keys and values when collecting storageState
• restore IndexedDB records by checking field presence instead of truthiness or nullish fallbacks
• add regression coverage for top-level falsy primitive values and out-of-line falsy keys

Why

storageState({ indexedDB: true }) treated serialized "trivial" values as truthy in both the collect and restore paths. That dropped valid values like 0, false, '', and null, and could also lose valid out-of-line keys like 0 and ''.

Impact

IndexedDB-backed auth and app state now round-trip correctly when records contain falsy primitive values or falsy out-of-line keys.

Testing

• npm test -- tests/library/browsercontext-storage-state.spec.ts --project=chromium-library --grep "should round-trip through the file|should round-trip top-level falsy IndexedDB primitives"
• npx eslint packages/injected/src/storageScript.ts tests/library/browsercontext-storage-state.spec.ts

[yury-s]

Please start with filing an issue. Also note that we are not accepting patches to this file, they should go into the browsers repo which is an open issue, #41551