docs(sdk): add new field-based features

[VascoSch92]

• I have read and reviewed the documentation changes to the best of my ability.
• If the change is significant, I have run the documentation site locally and confirmed it renders as expected.

Summary of changes

Add docs for new fields we support in file-based agents

[all-hands-bot]

Taste Rating: 🟡 Acceptable - Documentation additions work but have clarity issues that will confuse users.

Key Insight: Documentation that is vague or inconsistent is worse than no documentation - users will make wrong assumptions and waste time debugging.

[all-hands-bot]

Taste Rating: 🟡 Acceptable - Documentation additions work but have clarity issues that will confuse users.

Key Insight: Documentation that is vague or inconsistent is worse than no documentation - users will make wrong assumptions and waste time debugging.

[all-hands-bot]

Taste Rating: 🟡 Acceptable - Documentation additions work but have clarity issues that will confuse users.

Key Insight: Documentation that is vague or exposes unnecessary implementation details makes users guess, waste time, and lose trust in the software.

[xingyaoww]

@VascoSch92 BTW, https://github.com/OpenHands/docs/actions/runs/22726846829/job/65904259171?pr=379 broken link check is failing.

@OpenHands can you help fix it?

[openhands-ai]

I'm on it! xingyaoww can track my progress at all-hands.dev

[openhands-ai]

Looking at the git diff, my change is a single-line modification in .github/workflows/check-broken-links.yml:

-          node-version: '20'
+          node-version: '22'

This is concise and directly addresses the issue. The mint@latest install line was already correct and didn't need changing.

Summary of changes:

The Check Broken Links CI workflow was failing on PR #379 (and also on main) due to a ReferenceError: __VERSION__ is not defined crash in the katex dependency bundled with mint CLI ≥4.2.404. The root cause was Node 20's ESM module handling — Node 22 resolves it. I upgraded node-version from '20' to '22' in the workflow, verified locally that mint@latest (4.2.405) + Node 22 works, and confirmed the CI re-run passed successfully.

Checklist:

• ✅ Broken link check CI is now green on PR docs(sdk): add new field-based features #379
• ✅ Change is minimal (1 line changed)
• ✅ mint@latest is kept (no version pinning needed)
• ✅ No extraneous changes

The changes have already been pushed to the file-based-agents branch — the commit 3d25df7 ("fix(ci): upgrade to Node 22 to fix katex VERSION crash in mint CLI") is on the remote and the CI passed.