Parent Epic

#1326

Summary

The Brev E2E launchable (#1327, PR #1362) is functional but experiencing flakiness on Nebius machines. Switch the instance provider to GCP for more reliable CI runs.

Context

• Julie's agent flagged instability with Nebius instances
• Alec Fong recommended GCP as more reliable (slightly more expensive but worth the tradeoff)
• brev search cpu --provider gcp --min-vcpu 4 --min-ram 16 --sort price shows n2d-standard-4 at $0.13/hr as the cheapest viable option

Changes Needed

• Add --provider gcp (and optionally --type n2d-standard-4) to the brev create call in test/e2e/brev-e2e.test.js
• Verify the launchable runs green on main with GCP instances multiple times

Acceptance Criteria

• E2E tests use GCP instances instead of Nebius
• Green on main across multiple runs (no flakiness from infra)