CrossRelay stage 2: Codex /v1/responses relay, config.toml manager, Codex page

internal/config/config.go

@@ -48,6 +48,7 @@ type Provider struct {
 	APIKey           string    `json:"api_key"`
 	Models           Models    `json:"models"`
 	EnabledForClaude bool      `json:"enabled_for_claude"`
+	EnabledForCodex  bool      `json:"enabled_for_codex"`
 	CreatedAt        time.Time `json:"created_at"`
 }
 
@@ -63,8 +64,13 @@ type Config struct {
 	RelayToken     string     `json:"relay_token"`
 	Providers      []Provider `json:"providers"`
 	ActiveClaudeID string     `json:"active_claude_id,omitempty"`
-	Gateway        Gateway    `json:"gateway"`
-	Language       string     `json:"language"`
+	ActiveCodexID  string     `json:"active_codex_id,omitempty"`
+	// CodexPriorProvider remembers the model_provider value that was in
+	// config.toml before CrossRelay first applied, so restore can put it
+	// back instead of dropping the key.
+	CodexPriorProvider string  `json:"codex_prior_provider,omitempty"`
+	Gateway            Gateway `json:"gateway"`
+	Language           string  `json:"language"`
 }
 
 // ResolveModel maps the model name Claude Code asked for onto the model