fix(auth): normalize authMethod to lowercase on Kiro token import

- Add strings.ToLower() normalization in LoadKiroIDEToken()
- Add same normalization in LoadKiroTokenFromPath()
- Fixes issue where Kiro IDE exports "IdC" but code expects "idc"

internal/auth/kiro/aws.go

@@ -190,6 +190,9 @@ func LoadKiroIDEToken() (*KiroTokenData, error) {
 		return nil, fmt.Errorf("access token is empty in Kiro IDE token file")
 	}
 
+	// Normalize AuthMethod to lowercase (Kiro IDE uses "IdC" but we expect "idc")
+	token.AuthMethod = strings.ToLower(token.AuthMethod)
+
 	return &token, nil
 }
 
@@ -219,6 +222,9 @@ func LoadKiroTokenFromPath(tokenPath string) (*KiroTokenData, error) {
 		return nil, fmt.Errorf("access token is empty in token file")
 	}
 
+	// Normalize AuthMethod to lowercase (Kiro IDE uses "IdC" but we expect "idc")
+	token.AuthMethod = strings.ToLower(token.AuthMethod)
+
 	return &token, nil
 }