Zora coin metadata guide, and EVM and x402 on the turbo-upload page

[vilenarios]

Adds a guide for storing a Zora coin's metadata and image on Arweave with @ardrive/turbo-zora-uploader. The coin's metadata pointer is https://turbo-gateway.com/ITEM_ID, because Zora's create API accepts only an https or ipfs pointer, and media inside the metadata is ar://ITEM_ID. It also brings the turbo-upload page up to 0.7.0: EVM signing (ANS-104 type 3) and x402 uploads.

Merge after @ardrive/turbo-zora-uploader is published on npm. The guide links its npm page and installs it by name, and neither works until it is published. The guide matches the package at commit 340a3b9; if the package changes before publishing, re-sync the quickstart, testnet and browser samples. @ardrive/turbo-upload@0.7.0 is already on npm.

Merging deploys nothing: deploys are manual.

It also corrects a false claim on build/upload/x402-uploading-to-turbo: the unsigned x402 route has no free tier. An unpaid POST of five bytes to /v1/x402/upload/unsigned answers 402 with a USDC price; only signed items within the free tier upload free. The page also says that maxMUSDCAmount is optional, and that without it x402-fetch caps the price at 0.10 USDC. It says that x402-fetch is an optional peer you install. And it fixes the uploadRawX402Data sample, which passed a number where turbo-sdk 2.1.2 types maxMUSDCAmount as a BigNumber: the sample now uses new BigNumber(...) from bignumber.js 9. A BigNumber from another major version fails to type-check. The same free-tier claim lives in generated copies of the Turbo SDK README (sdks/turbo-sdk/(apis)/turboauthenticatedclient.mdx, sdks/turbo-sdk/llm.txt, public/sdks/turbo-sdk/llm.txt, public/llms-full.txt), which this PR does not edit: the fix belongs in the ardriveapp/turbo-sdk README, and the weekly regenerate run carries it here.

Needs your judgement

1. The pointer names one gateway. With the default uri: "auto", the metadata JSON returns https://turbo-gateway.com/ITEM_ID and every other file ar://ITEM_ID. Zora's create API refuses an ar:// pointer with HTTP 500, uri is required and needs to be an ipfs:// or https:// uri (checked on Base and Base Sepolia, with no transaction sent). turbo-gateway.com serves a fresh item at once as exactly application/json, so Zora's metadata check passes. The guide makes no claim about how Zora's app renders ar:// media.
2. A coin cannot be created from testnet uploads. The guide says so, dated 2026-10-15: ar-io.dev serves JSON with a charset, which fails Zora's check, and on Base Sepolia Zora's create API reverts the factory's coinAddress call. The uploads themselves work on testnet.
3. content/build/testnet/index.mdx said 105 KiB uploads free on testnet, where the same page and the live /v1/info say 5 MiB. The guide links this page, so this PR fixes that line.
4. Heading case. The guide's title is Title Case, to match its siblings in the sidebar, and its section headings are sentence case. On the turbo-upload page, the two new sections use Title Case to match the page.
5. content/sdks/index.mdx said turbo-upload is server-side only. The web build has shipped since 0.5.0, so this PR changes that sentence and widens the turbo-upload line.

What changed

• content/build/guides/zora-coin-metadata.mdx (new): when to use the uploader, install (with tsx), the package README's quickstart verbatim, who pays (signed free tier or x402 in USDC; the item limit is freeUploadLimitBytes in the upload service's /v1/info), the URLs it returns and why, private key, browser and smart-contract wallet signers, testnet, and the errors to catch.
• content/sdks/turbo-upload/index.mdx: EVM signers and x402 uploads sections, the comparison table (keys, browser support, size measured for 0.7.0), requirements, and the description.
• content/build/upload/x402-uploading-to-turbo.mdx: the unsigned-route correction described earlier.
• public/SKILL.md: an install line for each package, turbo-upload EVM and x402 recipes, and a Zora recipe matching the guide. public/llms.txt: one line for the guide (the file is hand-written; no generator touches it).
• content/build/testnet/index.mdx: the testnet free item size is 5 MiB.
• content/build/guides/meta.json and the guides landing page: list the guide. The folder sorts by title, so it lands last.

Not changed: content/sdks/turbo-upload/llm.txt, public/sdks/turbo-upload/llm.txt and public/llms-full.txt are generated, so the weekly regenerate run picks these edits up.

Checks

• npm run lint, npx tsc --noEmit: pass.
• npm run check-links: 344 files, 0 errors.
• npm run build: passes; the guide renders at /build/guides/zora-coin-metadata/ and sits last in the Guides sidebar.
• Every code sample in the guide and the new SKILL.md recipes type-checks against @zoralabs/coins-sdk@0.8.0, viem@2.53.1, @ardrive/turbo-upload@0.7.0 and the uploader packed from 340a3b9. The guide's quickstart, testnet and browser samples are byte-identical to the package README at 340a3b9. The x402 page's two turbo-sdk samples type-check against @ardrive/turbo-sdk@2.1.2.
• Run on testnet with a throwaway key:
  • The testnet sample returned ar:// for an image and the gateway URL for JSON.
  • The quickstart flow, with testnet: true on Base Sepolia, uploaded for free, and its metadata names the image as ar://. createCoin then failed Zora's check, as the guide says.
  • The guide's browser-wallet uploader, through an emulated wallet, also passed.
  • So did the turbo-upload EVM sample, its browser wallet wrapper and the SKILL.md EVM recipe.
• The turbo-upload x402 sample ran to the service's 402 quote and stopped before signing, so nothing was paid.
• The production quickstart ran up to reading coin.png, with no file present, so nothing was uploaded and no transaction was sent. No production upload or Base transaction was made from this PR.

🤖 Generated with Claude Code

https://claude.ai/code/session_015JYw2Nzv95CXaVZwUKS5n8