fix: show open project icon when project is already saved

The open project button was only visible for unsaved projects. Now it
displays in both states so users can always load a different project.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/components/Header.tsx

@@ -181,6 +181,25 @@ export function Header() {
                       </svg>
                     </button>
                   )}
+                  <button
+                    onClick={handleOpenFile}
+                    className="p-1.5 text-neutral-400 hover:text-neutral-200 hover:bg-neutral-800 rounded transition-colors"
+                    title="Open project"
+                  >
+                    <svg
+                      className="w-4 h-4"
+                      fill="none"
+                      viewBox="0 0 24 24"
+                      stroke="currentColor"
+                      strokeWidth={2}
+                    >
+                      <path
+                        strokeLinecap="round"
+                        strokeLinejoin="round"
+                        d="M2.25 12.75V12A2.25 2.25 0 014.5 9.75h15A2.25 2.25 0 0121.75 12v.75m-8.69-6.44l-2.12-2.12a1.5 1.5 0 00-1.061-.44H4.5A2.25 2.25 0 002.25 6v12a2.25 2.25 0 002.25 2.25h15A2.25 2.25 0 0021.75 18V9a2.25 2.25 0 00-2.25-2.25h-5.379a1.5 1.5 0 01-1.06-.44z"
+                      />
+                    </svg>
+                  </button>
                 </div>
 
                 {/* Settings - separated */}