chore(ci): extract helpers from brev-e2e beforeAll and remove phantom version field

Refactor test/e2e/brev-e2e.test.ts for issue #1390:

- Extract named helpers from the ~350-line monolithic beforeAll:
  cleanupLeftoverInstance(), createBrevInstance(), refreshAndWaitForSsh(),
  bootstrapLaunchable(), pollForSandboxReady(), writeManualRegistry().
  The beforeAll now reads as a high-level orchestration (~50 lines).

- Deduplicate brev create + error recovery: the deploy-cli and launchable
  paths shared duplicated brev refresh + waitForSsh patterns, now
  consolidated into refreshAndWaitForSsh().

- Remove phantom version: 1 from the manual registry write. The
  SandboxRegistry interface in src/lib/registry.ts has no version field;
  registerSandbox() doesn't write one either.

- bootstrapLaunchable() returns { remoteDir, needsOnboard } instead of
  mutating module-level state as a hidden side-effect.

- instanceCreated is set at call sites in beforeAll, not hidden inside
  createBrevInstance().

- Remove dead sleep() helper (defined but never called).

Pure refactoring — no behavior changes. // @ts-nocheck pragma preserved.

Note: PR #1791 (openshell-vm microVM) also touches this file — whoever
merges second will need a rebase.

Author: ericksoa