feat: add centralized test selectors constants file

Amp-Thread-ID: https://ampcode.com/threads/T-019c1359-48cc-7676-abc8-2de8c57b52cf
Co-authored-by: Amp <amp@ampcode.com>

browser_tests/fixtures/selectors.ts

@@ -0,0 +1,42 @@
+/**
+ * Centralized test selectors for browser tests.
+ * Use data-testid attributes for stable selectors.
+ */
+
+export const TestIds = {
+  sidebar: {
+    toolbar: 'side-toolbar',
+    nodeLibrary: 'node-library-tree',
+    nodeLibrarySearch: 'node-library-search',
+    workflows: 'workflows-sidebar',
+    themeToggle: 'theme-toggle'
+  },
+  tree: {
+    folder: 'tree-folder',
+    leaf: 'tree-leaf',
+    node: 'tree-node'
+  },
+  canvas: {
+    main: 'graph-canvas',
+    contextMenu: 'canvas-context-menu'
+  },
+  dialogs: {
+    settings: 'settings-dialog',
+    settingsContainer: 'settings-container',
+    confirm: 'confirm-dialog',
+    about: 'about-panel'
+  },
+  topbar: {
+    queueButton: 'queue-button'
+  }
+} as const
+
+/**
+ * Helper type for accessing nested TestIds
+ */
+export type TestIdValue =
+  | (typeof TestIds.sidebar)[keyof typeof TestIds.sidebar]
+  | (typeof TestIds.tree)[keyof typeof TestIds.tree]
+  | (typeof TestIds.canvas)[keyof typeof TestIds.canvas]
+  | (typeof TestIds.dialogs)[keyof typeof TestIds.dialogs]
+  | (typeof TestIds.topbar)[keyof typeof TestIds.topbar]