feat: Add system diagnostics command

Adds `weevil doctor` to check development environment health.
Reports status of Java, FTC SDK, Android SDK, ADB, and Gradle.
Provides clear next steps based on system state.

src/main.rs

@@ -33,6 +33,9 @@ enum Commands {
         android_sdk: Option<String>,
     },
     
+    /// Check system health and diagnose issues
+    Doctor,
+    
     /// Setup development environment (system or project)
     Setup {
         /// Path to project directory (optional - without it, sets up system)
@@ -105,6 +108,9 @@ fn main() -> Result<()> {
         Commands::New { name, ftc_sdk, android_sdk } => {
             commands::new::create_project(&name, ftc_sdk.as_deref(), android_sdk.as_deref())
         }
+        Commands::Doctor => {
+            commands::doctor::run_diagnostics()
+        }
         Commands::Setup { path } => {
             commands::setup::setup_environment(path.as_deref())
         }