eframe: ControlFlow stays Poll after redraws drain, loop spins at idle on Wayland

**Describe the bug**
On Linux/Wayland with eframe 0.35, the event loop does not return to Wait after a repaint burst drains. When no redraw is due, eframe sets no control flow, so the last Poll remains in effect. The loop then runs at zero timeout while idle. Captured on one app: about 16k notifier probe reads per second with one core busy. epoll wait times look normal throughout.

**To Reproduce**
1. Minimal eframe app on Wayland (winit 0.30). Request repaints in a burst, then stop.
2. Watch ControlFlow and CPU at idle. The loop stays in Poll.
3. `strace -k` points at the poller zero timeout path, not winit dispatch.

**Expected behavior**
No pending redraw means Wait. Poll holds only while redraws are due.

**Desktop:**
- OS: NixOS, native Wayland. Same binary with `WAYLAND_DISPLAY` unset returns to near zero CPU.
- Version: eframe 0.35. Not rechecked against main head.

**Additional context**
Local workaround is to set Wait when nothing is due. Idle returns to zero with that change. I have that as a small patch and will open a PR if you confirm the semantics. Related: rust-windowing/winit#4668 and #8314 (same Poll handling, resize trigger).

Start by locating eframe 0.35's native event-loop handling and the code that updates ControlFlow after repaint requests drain. Reproduce with a minimal Rust app on native Wayland, request a repaint burst, and observe ControlFlow and idle CPU; the fix is done when no pending redraw returns the loop to Wait and the idle loop no longer spins.

Written by the indexing model from the issue text.