feat: vscode extension (#59)

* feat: add initial VS Code extension plan and implementation tasks

* feat(vscode): added initial version of an Openchamber VSCode extension

* feat(vscode): enhance VS Code extension with theme integration and session management

* feat(vscode): implement connection status handling and overlay in VSCode layout

* feat: move extension to secondary sidebar

* chore: upgrade @opencode-ai/sdk to 1.0.150

* vscode: editor bridge, file picker, click-to-open in tool parts

* vscode: layout session lifecycle, theme sync, typography overrides

* ui: compact mode for vscode, model search, autocomplete width fixes

* perf: scroll force flag, raf placeholder, git polling backoff

* ui: tool output styling, markdown code block fix, gitignore

* refactor: update typography handling for VSCode runtime, remove unused styles

* docs: update README with VS Code extension details and add extension image

* docs: update changelog with new features and performance improvements

packages/vscode/webview/components/VSCodeHeader.tsx

@@ -0,0 +1,28 @@
+import React from 'react';
+
+interface VSCodeHeaderProps {
+  title: string;
+  showBack?: boolean;
+  onBack?: () => void;
+  actions?: React.ReactNode;
+}
+
+export function VSCodeHeader({ title, showBack, onBack, actions }: VSCodeHeaderProps) {
+  return (
+    <div className="flex items-center gap-2 px-3 py-2 border-b border-border bg-background/80 backdrop-blur-sm sticky top-0 z-10">
+      {showBack && (
+        <button
+          onClick={onBack}
+          className="p-1 -ml-1 rounded hover:bg-muted transition-colors"
+          aria-label="Go back"
+        >
+          <svg width="16" height="16" viewBox="0 0 16 16" fill="currentColor">
+            <path d="M11 2L5 8l6 6" stroke="currentColor" strokeWidth="1.5" fill="none" strokeLinecap="round" strokeLinejoin="round"/>
+          </svg>
+        </button>
+      )}
+      <h1 className="flex-1 text-sm font-medium truncate">{title}</h1>
+      {actions && <div className="flex items-center gap-1">{actions}</div>}
+    </div>
+  );
+}