Update npm deprecation notices to reflect current status

[fern-api]

Summary

npm classic tokens were permanently revoked on December 9, 2025. Updated the documentation to use time-robust language instead of referencing the mid-November 2025 date that has now passed.

Changes made:

• Updated 3 warning notices in publishing-to-npm.mdx to use present tense ("npm has deprecated") instead of future tense with specific dates

Also verified:

• Audited all 22 documented OpenAPI extensions against the Fern codebase - all are supported and implemented in fernExtensions.ts
• No deprecated or unsupported extensions found in the documentation

Review & Testing Checklist for Human

• Verify the updated npm deprecation language is accurate and doesn't reference outdated dates
• Check the preview link to confirm the warnings render correctly on the publishing page

Notes

The package-lock.json file that was accidentally added in the first commit has been removed.

Link to Devin run: https://app.devin.ai/sessions/2a965b5200d14bd0a7369d735bd83f3b
Requested by: Fern Support (info@buildwithfern.com)

[github-actions]

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[github-actions]

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