Fix: normalize Windows drive letter in VS Code extension webview paths (#1052)

Extract normalizeWindowsDriveLetter to shared pathUtils module

Normalize workspaceFolder to uppercase drive letter to match OpenCode
server's path normalization. This fixes session visibility issues
where VS Code extension sessions don't appear in CLI/desktop and vice
versa due to case-sensitive directory comparison on Windows.

Changes:
- Create pathUtils.ts with shared normalizeWindowsDriveLetter function
- Update opencode.ts to import from pathUtils instead of inline definition
- Update ChatViewProvider.ts, AgentManagerPanelProvider.ts,
  SessionEditorPanelProvider.ts to import from pathUtils

packages/vscode/src/AgentManagerPanelProvider.ts

@@ -6,12 +6,13 @@ import { getWebviewShikiThemes } from './shikiThemes';
 import { getWebviewHtml } from './webviewHtml';
 import { openSseProxy } from './sseProxy';
 import { resolveWebviewDevServerUrl } from './webviewDevServer';
+import { normalizeWindowsDriveLetter } from './pathUtils';
 
 export class AgentManagerPanelProvider {
   public static readonly viewType = 'openchamber.agentManager';
 
   private _panel?: vscode.WebviewPanel;
-  
+
   // Cache latest status/URL for when webview is resolved after connection is ready
   private _cachedStatus: ConnectionStatus = 'connecting';
   private _cachedError?: string;
@@ -54,10 +55,10 @@ export class AgentManagerPanelProvider {
     };
 
     this._panel.webview.html = this._getHtmlForWebview(this._panel.webview);
-    
+
     // Send theme payload (including optional Shiki theme JSON) after the webview is set up.
     void this.updateTheme(vscode.window.activeColorTheme.kind);
-    
+
     // Send cached connection status
     this._sendCachedState();
 
@@ -115,16 +116,16 @@ export class AgentManagerPanelProvider {
     // Cache the latest state
     this._cachedStatus = status;
     this._cachedError = error;
-    
+
     // Send to webview if it exists
     this._sendCachedState();
   }
-  
+
   private _sendCachedState() {
     if (!this._panel) {
       return;
     }
-    
+
     this._panel.webview.postMessage({
       type: 'connectionStatus',
       status: this._cachedStatus,
@@ -221,7 +222,9 @@ export class AgentManagerPanelProvider {
   }
 
   private _getHtmlForWebview(webview: vscode.Webview): string {
-    const workspaceFolder = vscode.workspace.workspaceFolders?.[0]?.uri.fsPath || '';
+    const workspaceFolder = normalizeWindowsDriveLetter(
+      vscode.workspace.workspaceFolders?.[0]?.uri.fsPath || ''
+    );
     const cliAvailable = this._openCodeManager?.isCliAvailable() ?? false;
 
     return getWebviewHtml({