refactor(app): replace tab drag handling with dndkit (#33880)

Co-authored-by: opencode-agent[bot] <219766164+opencode-agent[bot]@users.noreply.github.com>

packages/app/src/components/titlebar-tab-gesture.test.ts

@@ -0,0 +1,33 @@
+import { describe, expect, test } from "bun:test"
+import { canOpenTabRename, canStartTabDrag, forwardTabRef, isTabCloseTarget } from "./titlebar-tab-gesture"
+
+describe("titlebar tab gestures", () => {
+  test("excludes close controls from tab gestures", () => {
+    const close = document.createElement("div")
+    const button = document.createElement("button")
+    const link = document.createElement("a")
+    close.dataset.slot = "tab-close"
+    close.append(button)
+    expect(isTabCloseTarget(close)).toBe(true)
+    expect(isTabCloseTarget(button)).toBe(true)
+    expect(isTabCloseTarget(link)).toBe(false)
+  })
+
+  test("forwards component refs", () => {
+    const element = document.createElement("div")
+    let received: HTMLDivElement | undefined
+    forwardTabRef((value) => (received = value), element)
+    expect(received).toBe(element)
+  })
+
+  test("does not reopen rename while a save is pending", () => {
+    expect(canOpenTabRename(false, false, false)).toBe(true)
+    expect(canOpenTabRename(false, false, true)).toBe(false)
+  })
+
+  test("preserves native panning for touch pointers", () => {
+    expect(canStartTabDrag("mouse")).toBe(true)
+    expect(canStartTabDrag("pen")).toBe(true)
+    expect(canStartTabDrag("touch")).toBe(false)
+  })
+})