StoryWeave v0.10.0: credit preflight for long-form AI writing

I shipped StoryWeave v0.10.0 today.

This is a product update focused on making long-form AI writing more predictable before generation starts.

What changed:
- Chapter planning now shows estimated AI credit usage before generation starts.
- Scene Plan expansion checks available credits before running.
- If the estimate is insufficient, StoryWeave blocks the job before the model call and shows wallet top-up or plan upgrade guidance.
- Wallet balance is shown with estimated credit coverage, so authors can decide how much to recharge when they only need a small extra amount.
- Plan purchases now activate immediately when allowed.
- Same-tier and lower-tier plan purchases are blocked while active plan credits remain; wallet top-up is the intended path for short-term extra usage.

This came from testing real long-form generation flows. Longer projects, especially high-quality runs, need clearer cost visibility before the author starts a large job.

StoryWeave is still aimed at author-controlled fiction writing: plan the story, generate structure, draft with AI assistance when useful, review and edit manually, then save and export only the text the author approves.