docs: describe what the connection test actually requests on the connect-an-agent pages

[silentoplayz]

Summary

The cptr and Hermes pages said the connection test "checks basic connectivity, not model discovery". The test sends GET <URL>/models with the key and fails unless it returns HTTP 200, so a URL without /v1 normally fails the test itself. The troubleshooting entry now says what a passing test with no models means instead.

Related issue or discussion

None.

Checklist

• I have reviewed the relevant documentation and matched the existing style.
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Notes for reviewers

Sources on dev: routers/openai.py (the /verify route) and src/lib/apis/openai/index.ts.