Fix: banner on launch, config file loading, 7 providers match setup wizard

BUGFIXES:
- Banner now displays on 'gyandoot run' via gyandoot_tui::banner::print_banner()
- Config now loads from ~/.config/gyandoot/config.toml with fallback chain
  (XDG -> ~/.gyandoot/config.yaml -> hardcoded defaults), fixing 401 errors
- gyandoot init now writes visible placeholder api_key for users to edit

NEW PROVIDERS (4 added, now 7 total matching setup wizard):
- Google Gemini: Native API with x-goog-api-key auth, streamingGenerateContent
- DeepSeek: OpenAI-compatible wrapper at api.deepseek.com/v1
- OpenRouter: With HTTP-Referer/X-Title headers, model routing
- Groq: OpenAI-compatible wrapper at api.groq.com/openai/v1

All compile with 0 errors.

crates/gyandoot-providers/src/lib.rs

@@ -14,12 +14,20 @@ pub mod openai;
 pub mod anthropic;
 pub mod ollama;
 pub mod streaming;
+pub mod gemini;
+pub mod deepseek;
+pub mod openrouter;
+pub mod groq;
 
 // ─── Re-exports ───────────────────────────────────────────────────────────
 
 pub use openai::OpenAIProvider;
 pub use anthropic::AnthropicProvider;
 pub use ollama::OllamaProvider;
+pub use gemini::GeminiProvider;
+pub use deepseek::DeepSeekProvider;
+pub use openrouter::OpenRouterProvider;
+pub use groq::GroqProvider;
 pub use streaming::{SseParser, StreamEvent, TokenStream, collect_stream};
 
 // ─── ProviderResponse ─────────────────────────────────────────────────────
@@ -102,6 +110,7 @@ pub enum ProviderKind {
     Gemini,
     DeepSeek,
     OpenRouter,
+    Groq,
 }
 
 impl ProviderKind {
@@ -114,6 +123,7 @@ impl ProviderKind {
             "gemini" => Some(ProviderKind::Gemini),
             "deepseek" => Some(ProviderKind::DeepSeek),
             "openrouter" => Some(ProviderKind::OpenRouter),
+            "groq" => Some(ProviderKind::Groq),
             _ => None,
         }
     }
@@ -127,6 +137,7 @@ impl ProviderKind {
             ProviderKind::Gemini => "gemini",
             ProviderKind::DeepSeek => "deepseek",
             ProviderKind::OpenRouter => "openrouter",
+            ProviderKind::Groq => "groq",
         }
     }
 }
@@ -160,7 +171,7 @@ impl ProviderFactory {
         config: &gyandoot_core::ProviderRootConfig,
     ) -> ProviderResult<Box<dyn Provider>> {
         match kind {
-            ProviderKind::OpenAI | ProviderKind::DeepSeek | ProviderKind::OpenRouter => {
+            ProviderKind::OpenAI => {
                 let cfg = config.openai.as_ref().ok_or_else(|| gyandoot_core::ProviderError::Api {
                     status: 0,
                     message: "OpenAI config not found".to_string(),
@@ -196,8 +207,40 @@ impl ProviderFactory {
                     status: 0,
                     message: "Gemini config not found (use openai section)".to_string(),
                 })?;
-                // Gemini uses the OpenAI-compatible endpoint
-                Ok(Box::new(openai::OpenAIProvider::new(
+                Ok(Box::new(gemini::GeminiProvider::new(
+                    cfg.api_key.clone(),
+                    cfg.model.clone(),
+                    cfg.base_url.clone(),
+                )))
+            }
+            ProviderKind::DeepSeek => {
+                let cfg = config.openai.as_ref().ok_or_else(|| gyandoot_core::ProviderError::Api {
+                    status: 0,
+                    message: "DeepSeek config not found (use openai section)".to_string(),
+                })?;
+                Ok(Box::new(deepseek::DeepSeekProvider::new(
+                    cfg.api_key.clone(),
+                    cfg.model.clone(),
+                    cfg.base_url.clone(),
+                )))
+            }
+            ProviderKind::OpenRouter => {
+                let cfg = config.openai.as_ref().ok_or_else(|| gyandoot_core::ProviderError::Api {
+                    status: 0,
+                    message: "OpenRouter config not found (use openai section)".to_string(),
+                })?;
+                Ok(Box::new(openrouter::OpenRouterProvider::new(
+                    cfg.api_key.clone(),
+                    cfg.model.clone(),
+                    cfg.base_url.clone(),
+                )))
+            }
+            ProviderKind::Groq => {
+                let cfg = config.openai.as_ref().ok_or_else(|| gyandoot_core::ProviderError::Api {
+                    status: 0,
+                    message: "Groq config not found (use openai section)".to_string(),
+                })?;
+                Ok(Box::new(groq::GroqProvider::new(
                     cfg.api_key.clone(),
                     cfg.model.clone(),
                     cfg.base_url.clone(),
@@ -220,7 +263,7 @@ impl ProviderFactory {
 
         let config = gyandoot_core::ProviderRootConfig {
             default: name.to_string(),
-            openai: if matches!(kind, ProviderKind::OpenAI | ProviderKind::DeepSeek | ProviderKind::OpenRouter | ProviderKind::Gemini) {
+            openai: if matches!(kind, ProviderKind::OpenAI | ProviderKind::DeepSeek | ProviderKind::OpenRouter | ProviderKind::Gemini | ProviderKind::Groq) {
                 Some(gyandoot_core::OpenAIConfig {
                     api_key: api_key.to_string(),
                     model: model.to_string(),
@@ -263,6 +306,7 @@ fn default_base_url(kind: &ProviderKind) -> String {
         ProviderKind::Gemini => "https://generativelanguage.googleapis.com/v1".to_string(),
         ProviderKind::DeepSeek => "https://api.deepseek.com/v1".to_string(),
         ProviderKind::OpenRouter => "https://openrouter.ai/api/v1".to_string(),
+        ProviderKind::Groq => "https://api.groq.com/openai/v1".to_string(),
     }
 }
 
@@ -281,6 +325,7 @@ mod tests {
             ProviderKind::Gemini,
             ProviderKind::DeepSeek,
             ProviderKind::OpenRouter,
+            ProviderKind::Groq,
         ] {
             let s = kind.to_string();
             let parsed = ProviderKind::from_str(&s).unwrap();