docs(readme): lead with creative results and simplify onboarding

[georgi]

Summary

The README introduces source builds before showing enough of the creative workflow, and repeats setup instructions across several sections.

• Move the product description and download links above the hero image, and bring the editable film workflow and recipes ahead of source setup.
• Give Studio onboarding a named bundled example and a preview action, with provider setup deferred until generation.
• Consolidate developer setup and repeated billing prose while preserving paid-call warnings and existing section anchors.

Test plan

• git diff --check passed.
• Checked all 33 local file/image links and heading anchors, plus control characters.
• npm run test:affected passed with no tests selected for the README-only diff.
• Cross-checked the named storyboard fixture and Preview control against repository source; reviewed film steps against the quick-start guide.
• No application code changed. The desktop flow was not run interactively.