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.

src/main.rs

@@ -178,14 +178,13 @@ fn default_config_dir() -> PathBuf {
 
 /// Run the agent in the given platform mode
 async fn cmd_run(profile_name: &str, platform: &str, prompt: Option<&str>) -> anyhow::Result<()> {
+    // Print the banner on launch
+    gyandoot_tui::banner::print_banner();
+
     tracing::info!("Running agent (profile={}, platform={})", profile_name, platform);
 
-    // Load config via resolver
-    let resolver = gyandoot_profile::ConfigResolver::default();
-    let _resolved = resolver.resolve();
-
-    // Initialize the agent loop using gyandoot-core config
-    let config = gyandoot_core::config::AgentConfig::default();
+    // Load config from user config files, falling back to defaults
+    let config = load_agent_config();
     let agent = gyandoot_agent::agent_loop::AgentLoop::new(config);
 
     if let Some(p) = prompt {
@@ -196,6 +195,51 @@ async fn cmd_run(profile_name: &str, platform: &str, prompt: Option<&str>) -> an
     Ok(())
 }
 
+/// Load agent config from user config files with fallback to defaults.
+///
+/// Resolution order:
+/// 1. `~/.config/gyandoot/config.toml` (XDG primary)
+/// 2. `~/.gyandoot/config.yaml` (legacy)
+/// 3. `AgentConfig::default()` (hardcoded defaults)
+fn load_agent_config() -> gyandoot_core::config::AgentConfig {
+    // 1. Try XDG-style config: ~/.config/gyandoot/config.toml
+    if let Some(cfg_dir) = dirs::config_dir() {
+        let xdg_path = cfg_dir.join("gyandoot").join("config.toml");
+        if xdg_path.exists() {
+            match gyandoot_core::config::ConfigLoader::from_file(&xdg_path) {
+                Ok(gyandoot_cfg) => {
+                    tracing::info!("Loaded config from {}", xdg_path.display());
+                    return gyandoot_core::config::AgentConfig::from(gyandoot_cfg);
+                }
+                Err(e) => tracing::warn!("Failed to parse {}: {}", xdg_path.display(), e),
+            }
+        }
+    }
+
+    // 2. Try legacy config: ~/.gyandoot/config.yaml
+    if let Some(home) = dirs::home_dir() {
+        let legacy_path = home.join(".gyandoot").join("config.yaml");
+        if legacy_path.exists() {
+            match std::fs::read_to_string(&legacy_path) {
+                Ok(contents) => {
+                    match serde_yaml::from_str::<gyandoot_core::config::GyandootConfig>(&contents) {
+                        Ok(gyandoot_cfg) => {
+                            tracing::info!("Loaded config from {}", legacy_path.display());
+                            return gyandoot_core::config::AgentConfig::from(gyandoot_cfg);
+                        }
+                        Err(e) => tracing::warn!("Failed to parse {}: {}", legacy_path.display(), e),
+                    }
+                }
+                Err(e) => tracing::warn!("Failed to read {}: {}", legacy_path.display(), e),
+            }
+        }
+    }
+
+    // 3. Fallback to hardcoded defaults
+    tracing::warn!("No config file found; using default configuration (API keys will be empty)");
+    gyandoot_core::config::AgentConfig::default()
+}
+
 /// Start the gateway server for multi-platform sessions
 async fn cmd_serve(profile_name: &str, host: &str, port: u16) -> anyhow::Result<()> {
     tracing::info!(
@@ -238,7 +282,7 @@ system_prompt = "You are GyanDoot, an AI Agent Platform."
 default = "openai"
 
 [providers.openai]
-api_key = ""
+api_key = "sk-your-api-key-here"
 model = "gpt-4o"
 
 [platform]