Problem

github/mod.rs indexes into serde_json::Value with patterns like pr_resp["head"]["sha"].as_str().unwrap_or(""). If the API returns an error JSON, this silently produces empty strings.

Proposed Solution

Define #[derive(Deserialize)] structs for PR, CheckRun, Issue responses. Errors surface at deserialization time with clear messages. Use #[serde(default)] for optional fields.

Category: enhancement | Priority: medium