docs: document per-script disable-sri for remote js scripts

[devin-ai-integration]

Summary

Documents the new per-script disable-sri option for remote js scripts in docs.yml. Fern adds a Subresource Integrity (SRI) integrity attribute (plus crossorigin) to remote scripts by default; disable-sri: true opts a specific script out so it renders without integrity, for scripts whose content changes at the same URL.

Changes:

• custom-css-js.mdx: new ### Subresource integrity subsection under Custom JavaScript, briefly explaining SRI and the disable-sri opt-out with a docs.yml snippet:

  js:
    - url: https://cdn.example.com/a.js
      disable-sri: true # rendered without an integrity attribute
    - url: https://cdn.example.com/b.js # still gets SRI (default)

• changelog/2026-07-15.mdx: Docs changelog entry (customization, docs.yml, security) linking to the new section.

Documents the feature shipped in fern-api/fern#17060, fern-api/fern#17071, and fern-api/fern-platform#13119. No SDK changelog entries.

Validated with fern check --warnings (0 errors) and pre-commit/Vale (0 errors, 0 warnings on the new content).

Link to Devin session: https://app.devin.ai/sessions/64da49a5625a4477ac4bc635b19b4d73

[devin-ai-integration]

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[github-actions]

🌿 Preview your docs: https://fern-preview-devin-1784135298-disable-sri-docs.docs.buildwithfern.com/learn

Here are the markdown pages you've updated:

• learn/docs/changelog/2026/7/15
• learn/docs/customization/custom-css-js