feat(config): add default Kiro model aliases for standard Claude model names

Kiro models are exposed with kiro- prefix (e.g., kiro-claude-sonnet-4-5),
which prevents clients like Claude Code from using standard model names
(e.g., claude-sonnet-4-20250514).

This change injects default oauth-model-alias entries for the kiro channel
when no user-configured aliases exist, following the same pattern as the
existing Antigravity defaults. The aliases map standard Claude model names
(both with and without date suffixes) to their kiro-prefixed counterparts.

Default aliases added:
- claude-sonnet-4-5-20250929 / claude-sonnet-4-5 → kiro-claude-sonnet-4-5
- claude-sonnet-4-20250514 / claude-sonnet-4 → kiro-claude-sonnet-4
- claude-opus-4-6 → kiro-claude-opus-4-6
- claude-opus-4-5-20251101 / claude-opus-4-5 → kiro-claude-opus-4-5
- claude-haiku-4-5-20251001 / claude-haiku-4-5 → kiro-claude-haiku-4-5

All aliases use fork: true to preserve the original kiro-* names.
User-configured kiro aliases are respected and not overridden.

Closes router-for-me/CLIProxyAPIPlus#208

internal/config/config.go

@@ -736,8 +736,32 @@ func payloadRawString(value any) ([]byte, bool) {
 // SanitizeOAuthModelAlias normalizes and deduplicates global OAuth model name aliases.
 // It trims whitespace, normalizes channel keys to lower-case, drops empty entries,
 // allows multiple aliases per upstream name, and ensures aliases are unique within each channel.
+// It also injects default aliases for channels that have built-in defaults (e.g., kiro)
+// when no user-configured aliases exist for those channels.
 func (cfg *Config) SanitizeOAuthModelAlias() {
-	if cfg == nil || len(cfg.OAuthModelAlias) == 0 {
+	if cfg == nil {
+		return
+	}
+
+	// Inject default Kiro aliases if no user-configured kiro aliases exist
+	if cfg.OAuthModelAlias == nil {
+		cfg.OAuthModelAlias = make(map[string][]OAuthModelAlias)
+	}
+	if _, hasKiro := cfg.OAuthModelAlias["kiro"]; !hasKiro {
+		// Check case-insensitive too
+		found := false
+		for k := range cfg.OAuthModelAlias {
+			if strings.EqualFold(strings.TrimSpace(k), "kiro") {
+				found = true
+				break
+			}
+		}
+		if !found {
+			cfg.OAuthModelAlias["kiro"] = defaultKiroAliases()
+		}
+	}
+
+	if len(cfg.OAuthModelAlias) == 0 {
 		return
 	}
 	out := make(map[string][]OAuthModelAlias, len(cfg.OAuthModelAlias))