## Why
Ollama requests need to honor Codex's configured outbound proxy policy and custom CA handling.
## What changed
- Replace Ollama's direct `reqwest` client with a route-aware client created by `codex-http-client`.
- Preserve the five-second connection timeout and legacy system-root fallback for default-routed requests.
- Reuse one Ollama client for connectivity, version, model discovery, and model-pull checks.
- Surface HTTP transport initialization errors instead of replacing them with the generic Ollama connection error.
## Testing
- Cover system-proxy routing and invalid `CODEX_CA_CERTIFICATE` and `SSL_CERT_FILE` values under both outbound proxy policies.
- Verify that version and model checks reuse the existing Ollama client.
GitOrigin-RevId: c7cc36845a9bceb57ce5524b9e1b3cbe317897a3
Celia Chen
7d5253d2b0