Fix build and warnings - #78

- winit 0.30: EventLoop::run is deprecated, so Ui::run's closure becomes a
  UiApp ApplicationHandler driven by run_app. Pure mechanical move —
  run_app is literally run() with a dispatch closure, same events.
- raw-window-handle 0.6: HasRawWindowHandle/raw_window_handle() are
  deprecated; use HasWindowHandle + window_handle().as_raw().
- unused mut in mips_cache_v2 (only opcodefusion writes prev_s1) and in
  main.rs (only the pcap prompt writes cfg).
- coffdump's Fdr/Pdr mirror on-disk records: allow(dead_code).
- drop the unused SOCKET_FILTERS const in iris-gui.

Co-Authored-By: Claude Opus 5 (1M context) <[email protected]>

--features r5k,r5ksc_triton has not compiled since the Triton L2-enable sync
landed: `cache` needs to be mut for set_l2_enabled. Only that feature writes
it, so the mut is paired with a cfg'd allow(unused_mut).

Also silence unreachable_code on idle_state, which follows the jit
dispatch's return when both features are on (iris-gui's premiere build).

Co-Authored-By: Claude Opus 5 (1M context) <[email protected]>