Add @sei-js/x402 docs

[codebycarson]

All docs for @sei-js packages need to live in this repo, regardless of whether the packages code actually lives here. This PR adds all the docs for @sei-js/x402 and all it's sub packages.

• Copied over the docs from the main x402 repo, added pages for each facilitator, and improved the flow of the files.
• Removed any references to Base

[changeset-bot]

⚠️ No Changeset found

Latest commit: 1541b2a

Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.

This PR includes no changesets

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[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (0707a2e) to head (1541b2a).
⚠️ Report is 26 commits behind head on main.

Additional details and impacted files

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  Coverage   100.00%   100.00%           
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  Files           73        73           
  Lines          855       855           
  Branches       139       139           
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  Hits           855       855           

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[Copilot]

Pull Request Overview

This PR adds comprehensive documentation for the @sei-js/x402 package ecosystem to the docs repository. It introduces complete documentation for the x402 HTTP micropayment protocol including quickstart guides, package documentation, facilitator setup guides, and client integration examples.

• Adds x402 protocol documentation with overview, quickstart guide, and architectural details
• Documents all x402 package integrations (Express, Hono, Next.js, Fetch, Axios)
• Includes facilitator setup guide and client integration examples

Reviewed Changes

Copilot reviewed 13 out of 13 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
docs/x402/quickstart.mdx	Quickstart guide for building paid APIs with x402
docs/x402/packages/*.mdx	Documentation for all x402 package integrations
docs/x402/overview.mdx	Protocol architecture and component overview
docs/x402/introduction.mdx	Main introduction page for x402 on Sei
docs/x402/facilitators/*.mdx	Facilitator setup and example implementation
docs/x402/clients/fetch.mdx	Client integration guide for Fetch API
docs/docs.json	Navigation structure for x402 documentation

Comments suppressed due to low confidence (3)

docs/x402/packages/x402-next.mdx:28

• Network name 'pacific-1' is inconsistent with the Sei testnet chain ID mentioned in quickstart.mdx (1328). Consider using consistent network identifiers throughout the documentation.

      network: "pacific-1",

docs/x402/packages/x402-hono.mdx:30

• Network name 'pacific-1' is inconsistent with the Sei testnet reference in other files. Ensure network naming is consistent across all documentation.

      network: "pacific-1",

docs/x402/packages/x402-express.mdx:30

• Network name 'pacific-1' is inconsistent with the Sei testnet reference in other files. Ensure network naming is consistent across all documentation.

      network: "pacific-1",