test: comprehensive properties panel E2E tests (PNL-01) (#10548)

## Summary
Comprehensive Playwright E2E tests for the properties panel (right
sidebar).

Part of the **Test Coverage Q2 Overhaul** initiative (Phase 2: PNL-01).

## What's included
- **PropertiesPanelHelper** page object in `browser_tests/helpers/` —
locators + action methods for all panel elements
- **35 test cases** covering:
  - Open/close via actionbar toggle
- Workflow Overview (no selection): tabs, title, nodes list, global
settings
  - Single node selection: title, parameters, info tab, widgets display
  - Multi-node selection: item count, node listing, hidden Info tab
  - Title editing: pencil icon, edit mode, rename, visibility rules
  - Search filtering: query, clear, empty state
- Settings tab: Normal/Bypass/Mute state, color swatches, pinned toggle
  - Selection transitions: no-selection ↔ single ↔ multi
  - Nodes tab: list all, search filter
  - Tab label changes based on selection count
  - **Errors tab scaffold** (for @jaeone94 ADD-03)

## Testing
- All tests use Vue nodes with new menu enabled
- Zero flaky tests (proper waits, no sleeps)
- Screenshots scoped to panel elements

## Unblocks
- **ADD-03** (error systems by @jaeone94) — errors tab scaffold ready to
extend

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-10548-test-comprehensive-properties-panel-E2E-tests-PNL-01-32f6d73d36508199a216fd8d953d8e18)
by [Unito](https://www.unito.io)

---------

Co-authored-by: GitHub Action <action@github.com>

browser_tests/tests/propertiesPanel/PropertiesPanelHelper.ts

@@ -0,0 +1,100 @@
+import type { Locator, Page } from '@playwright/test'
+import { expect } from '@playwright/test'
+
+import { TestIds } from '../../fixtures/selectors'
+
+export class PropertiesPanelHelper {
+  readonly root: Locator
+  readonly panelTitle: Locator
+  readonly searchBox: Locator
+  readonly closeButton: Locator
+
+  constructor(readonly page: Page) {
+    this.root = page.getByTestId(TestIds.propertiesPanel.root)
+    this.panelTitle = this.root.locator('h3')
+    this.searchBox = this.root.getByPlaceholder(/^Search/)
+    this.closeButton = this.root.locator('button[aria-pressed]')
+  }
+
+  get tabs(): Locator {
+    return this.root.locator('nav button')
+  }
+
+  getTab(label: string): Locator {
+    return this.root.locator('nav button', { hasText: label })
+  }
+
+  get titleEditIcon(): Locator {
+    return this.panelTitle.locator('i[class*="lucide--pencil"]')
+  }
+
+  get titleInput(): Locator {
+    return this.root.getByTestId(TestIds.node.titleInput)
+  }
+
+  getNodeStateButton(state: 'Normal' | 'Bypass' | 'Mute'): Locator {
+    return this.root.locator('button', { hasText: state })
+  }
+
+  getColorSwatch(colorName: string): Locator {
+    return this.root.locator(`[data-testid="${colorName}"]`)
+  }
+
+  get pinnedSwitch(): Locator {
+    return this.root.locator('[data-p-checked]').first()
+  }
+
+  get subgraphEditButton(): Locator {
+    return this.root.locator('button:has(i[class*="lucide--settings-2"])')
+  }
+
+  get contentArea(): Locator {
+    return this.root.locator('.scrollbar-thin')
+  }
+
+  get errorsTabIcon(): Locator {
+    return this.root.locator('nav i[class*="lucide--octagon-alert"]')
+  }
+
+  get viewAllSettingsButton(): Locator {
+    return this.root.getByRole('button', { name: /view all settings/i })
+  }
+
+  get collapseToggleButton(): Locator {
+    return this.root.locator(
+      'button:has(i[class*="lucide--chevrons-down-up"]), button:has(i[class*="lucide--chevrons-up-down"])'
+    )
+  }
+
+  async open(actionbar: Locator): Promise<void> {
+    if (!(await this.root.isVisible())) {
+      await actionbar.click()
+      await expect(this.root).toBeVisible()
+    }
+  }
+
+  async close(): Promise<void> {
+    if (await this.root.isVisible()) {
+      await this.closeButton.click()
+      await expect(this.root).not.toBeVisible()
+    }
+  }
+
+  async switchToTab(label: string): Promise<void> {
+    await this.getTab(label).click()
+  }
+
+  async editTitle(newTitle: string): Promise<void> {
+    await this.titleEditIcon.click()
+    await this.titleInput.fill(newTitle)
+    await this.titleInput.press('Enter')
+  }
+
+  async searchWidgets(query: string): Promise<void> {
+    await this.searchBox.fill(query)
+  }
+
+  async clearSearch(): Promise<void> {
+    await this.searchBox.fill('')
+  }
+}