feat(Common): Add TreeView error and StatusBar proxy target

- Added `Serialize` and `Deserialize` to `CommonError` to enable IPC transmission of errors across `Mountain`↔`Cocoon` boundaries via `Vine` gRPC layer, ensuring structured error handling in extension workflows
- Introduced `TreeViewProviderNotFound` error variant to support TreeView API implementation in `Cocoon` sidecar (MVP Path A), aligning with implemented workflow #11
- Added `ExtHostStatusBar` variant to `ProxyTarget` enum to enable RPC routing for Status Bar API through `Track` dispatcher, extending extension host capabilities
- Simplified `tauri::Error` conversion to maintain clean error handling in Tauri↔`Wind` IPC (`Echo` layer)

These changes expand extension API support in `Cocoon` while strengthening error propagation mechanisms in Land's core IPC architecture.

Author: NikolaRHristov

Source/Error/CommonError.rs

@@ -5,12 +5,13 @@
 
 use std::path::PathBuf;
 
+use serde::{Deserialize, Serialize};
 use thiserror::Error;
 
 /// A common error enum for the application, encompassing all major categories
 /// of failures that can occur during the execution of effects or other
-/// operations.
-#[derive(Error, Debug, Clone)]
+// operations.
+#[derive(Error, Debug, Clone, Serialize, Deserialize)]
 pub enum CommonError {
 	// --- FileSystem Errors ---
 	#[error("FileSystem I/O error for '{Path}': {Description}")]
@@ -65,6 +66,10 @@ pub enum CommonError {
 	#[error("Language provider '{ProviderIdentifier}' invocation failed: {Reason}")]
 	ProviderInvocation { ProviderIdentifier:String, Reason:String },
 
+	// --- TreeView Errors (New) ---
+	#[error("TreeView provider not found for view ID '{ViewIdentifier}'")]
+	TreeViewProviderNotFound { ViewIdentifier:String },
+
 	// --- Other Specific Errors ---
 	#[error("External service '{ServiceName}' failed: {Description}")]
 	ExternalServiceError { ServiceName:String, Description:String },
@@ -120,9 +125,5 @@ impl From<serde_json::Error> for CommonError {
 /// Converts a `tauri::Error` into a `CommonError`. This is useful for
 /// handling errors from Tauri's APIs within our effect system.
 impl From<tauri::Error> for CommonError {
-	fn from(TauriError:tauri::Error) -> Self {
-		// We can categorize some Tauri errors, but for now, a general
-		// UserInterfaceInteraction or IPC error is sufficient.
-		CommonError::UserInterfaceInteraction { Reason:TauriError.to_string() }
-	}
+	fn from(TauriError:tauri::Error) -> Self { CommonError::UserInterfaceInteraction { Reason:TauriError.to_string() } }
 }

Source/IPC/DTO/ProxyTarget.rs

@@ -110,6 +110,8 @@ pub enum ProxyTarget {
 
 	ExtHostTreeView,
 
+	ExtHostStatusBar,
+
 	ExtHostSourceControlManagement,
 
 	ExtHostTesting,
@@ -118,7 +120,6 @@ pub enum ProxyTarget {
 impl ProxyTarget {
 	/// Returns a string prefix representing the target, used in constructing
 	/// fully qualified RPC method names (e.g.,
-
 	/// `MainThreadCommands$ExecuteCommand`).
 	pub fn GetTargetPrefix(&self) -> String { format!("{:?}", self) }
 }