Document credential file placement - #573

Summary

Docs for credential file placement. Draft until API version 2026-11-01 is released and agent 0.72.0 ships.

• New page platform/credential-files.mdx (Platform → Credential Files):
  • the per-platform files object, with a PostgreSQL credential on Linux and a service account on Windows;
  • windowsStore: false;
  • a field reference;
  • the rules the API enforces;
  • the Windows defaults: SYSTEM keeps full control, Administrators can be lowered but not removed, and NT SERVICE\ accounts resolve only once installed;
  • how the agent writes files: atomically, key first, no folders created, old files left in place;
  • compatibility with earlier API versions, the 2023-11-01 workload backport, and agents before 0.72.0.
• Troubleshooting guide: a new "Credential files not written" section. It covers the step-agent status last-report line and Windows events 800 and 801, with a table of the fault values and their fixes.

vale and markdown-link-check add nothing new. The remaining vale warnings on the troubleshooting page were already there, and so were its two broken image links.

Still to do once 2026-11-01 is released: point platform/smallstep-api.mdx at it, and add release notes.

Related PRs

• smallstep/protobufs#804, smallstep/api#155, smallstep/gateway#629, smallstep/mission-control#359, smallstep/agent#1271, smallstep/web#3162, smallstep/robot#213

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