test(e2e): browser signup lands on a workspace and creates a first workbench (CL-9567)

[TheGreatAxios]

Summary

• Adds e2e/browser/first-run.test.ts: a fresh user signs up in real Chrome, the client provisions its workspace over stock routes, connects an Anthropic placeholder key (stored only, never called), lands on the new-workbench prompt, starts a workbench, and sees it in the sidebar Workbenches group. UI-visible assertions only.
• Fixes the browser harness (separate commit): the hub was served without its WebSocket handler and on the wrong port, so the in-process sidecar could never connect and onboarding hung on "Getting Myra ready".

Bugs found

• Harness only (fixed): WebSocket upgrade not forwarded + PORT unset. No apps/web bug found; the flow works end to end.
• Not fixed: the test DB persists across runs, so each run signs up a unique alice+<ts>@example.com. A workspace with no workbenches lands directly on /new.
• Observed, not addressed: hub log still shows periodic Workflow probe cleanup reconciliation errors and sidecar WebSocket reconnect warnings after the test.

Resolves CL-9567

[linear-code]

CL-9567