Previously, when secret deployment options like CODER_OIDC_CLIENT_SECRET
were populated, the API correctly returned the "secret": "true"
annotation, but the UI did not indicate that these secrets were
configured. The UI would show "Not set" regardless of whether the
secret was set or not.

Now, the UI checks both the secret annotation and the value_source
field. When a secret is configured (value_source is set), it displays
"Set" to indicate the secret is populated. When a secret is not
configured, it displays "Not set".

Fixes #18913

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>