[codex] center docs content and update editor link

[arthurgervais]

/claim tscircuit/docs-old#64
/claim tscircuit/docs-old#67

Summary

• center the docs content column after the table of contents is hidden, matching the archived docs-centering bounty request
• change the navbar CTA from Use Online to Try Online
• point the CTA directly at https://tscircuit.com/editor

Bounty context

Archived bounty issues:

• Docs are not properly centered docs-old#64
• Find Packages link on docs should say "Try Online" and go to tscircuit.com/editor docs-old#67

tscircuit/docs-old is archived/read-only, so I could not comment /attempt there before opening this PR.

Verification

• npx biome format docusaurus.config.ts src/css/custom.css src/theme/DocItem/Layout/styles.module.css
• npm run typecheck
• git diff --check HEAD~1..HEAD
• npm run docusaurus -- build after aligning local npm verification to the repo lockfile's webpack@5.101.3
• served the built site locally and checked with Puppeteer that the navbar contains Try Online -> https://tscircuit.com/editor and the docs column is constrained to 1000px in the main docs area

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Project	Deployment	Actions	Updated (UTC)
docs	Ready	Preview, Comment	May 20, 2026 11:14pm