[review only] fix(config): recognize platform hint override keys

[WolframRavenwolf]

Review-only purpose

This draft PR exists only to give the exact public candidate a stable automated-review surface. It is not intended for merge into the fork.

• Candidate targets upstream Hermes Agent main.
• Base branch is pinned to the candidate's exact upstream parent.
• Public diff is limited to config-key validation and focused tests.
• The real upstream PR will be opened only after local, independent, and Devin review gates pass.