Cherry-picks two cleanup PRs and finishes the job. Net 262 deletions.
- #1473 (@abhay-codes07): drops a `console.log` in the fullscreen note editor that printed the whole note body on every keystroke, which PostHog session replay can capture.
- #1563 (@ishaanxgupta): removes `/api/onboarding/research` and `/api/onboarding/extract-content`. Neither has a caller anywhere in the repo, and both spent metered Exa and xAI quota. This reverts the guards added for them in #1589, which only existed to make unreachable code safe.
- On top: `EXA_API_KEY`, `XAI_API_KEY` and the `@ai-sdk/xai` dependency are removed, since deleting those routes left them with no consumer.
Co-Authored-By: abhay-codes07 <182421137+abhay-codes07@users.noreply.github.com>
Co-Authored-By: ishaanxgupta <124028055+ishaanxgupta@users.noreply.github.com>
