fix(google): lazy-load jose in CJS auth helpers

[fahe1em1]

Summary

• lazy-load jose inside the GCP auth helpers so the CJS bundle no longer eagerly require() an ESM-only dependency
• keep the ESM path unchanged while fixing CommonJS consumers of @langchain/google/node
• add focused regression tests that prove the helper module loads without importing jose until a signing helper is actually used

Fixes #10403.

Why this is safe

This only changes when jose is loaded. The affected helpers were already async, so switching them to fetch jose lazily preserves behavior while avoiding the ERR_REQUIRE_ESM crash in CommonJS runtimes.

Validation

• pnpm --filter @langchain/google test -- src/utils/tests/gcp-auth.test.ts
• pnpm --filter @langchain/google build
• pnpm --filter @langchain/google lint

[changeset-bot]

🦋 Changeset detected

Latest commit: ad6cafd

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
@langchain/google	Patch

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[Allen Firstenberg (afirstenberg)]

LGTM

[pawel-twardziak]

great work fahe1em1 !