zagent 0.0.231

• zagent quota errors now say WHICH problem they are: a rejected or
  missing credential is a "sign-in problem" that names the fix (zagent login or ZAI_API_KEY); HTTP 429 and business codes 1308/1113 are a
  "quota-window problem" that point at the reset and quota reset
  tickets; transport failures are named network problems. The same
  classification reaches quota balance|preview|reset (flock finding
  F11).
• quota status/usage now also resolve the Coding Plan key that
  zagent login provisions into ~/.zcode/v2/provider_config.json
  (new keySource: "provider-config") — signing in fixes quota on the
  first retry instead of needing another zagent run to materialize
  the key. A CLI config whose provider key is still empty falls through
  to the provisioned key instead of erroring.