fix(doctor): parse oauth profile syntax before provider validation

The doctor's config validation was rejecting valid fallback providers
using OAuth multi-profile syntax (e.g. "gemini:profile-1") because it
passed the full string to create_provider. Now strips the profile
suffix via parse_provider_profile before validation.

Also promotes parse_provider_profile to pub(crate) visibility so the
doctor module can access it.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/doctor/mod.rs

@@ -616,7 +616,10 @@ fn check_config_semantics(config: &Config, items: &mut Vec<DiagItem>) {
 }
 
 fn provider_validation_error(name: &str) -> Option<String> {
-    match crate::providers::create_provider(name, None) {
+    // Parse OAuth multi-profile syntax before validation
+    let (provider_name, _profile) = crate::providers::parse_provider_profile(name);
+
+    match crate::providers::create_provider(provider_name, None) {
         Ok(_) => None,
         Err(err) => Some(
             err.to_string()
@@ -1143,6 +1146,18 @@ mod tests {
         assert_eq!(fb_item.unwrap().severity, Severity::Warn);
     }
 
+    #[test]
+    fn config_validation_accepts_oauth_profiles() {
+        let mut config = Config::default();
+        config.reliability.fallback_providers = vec!["gemini:profile-1".into()];
+        let mut items = Vec::new();
+        check_config_semantics(&config, &mut items);
+        // Should NOT warn about valid provider with profile syntax
+        assert!(!items
+            .iter()
+            .any(|i| { i.severity == Severity::Warn && i.message.contains("gemini") }));
+    }
+
     #[test]
     fn config_validation_warns_bad_custom_fallback() {
         let mut config = Config::default();

src/providers/mod.rs

@@ -1362,7 +1362,7 @@ fn create_provider_with_url_and_options(
 /// delimited profile, or `(original_str, None)` otherwise.  Entries starting
 /// with `custom:` or `anthropic-custom:` are left untouched because the colon
 /// is part of the URL scheme.
-fn parse_provider_profile(s: &str) -> (&str, Option<&str>) {
+pub(crate) fn parse_provider_profile(s: &str) -> (&str, Option<&str>) {
     if s.starts_with("custom:") || s.starts_with("anthropic-custom:") {
         return (s, None);
     }