warp: SELECT opens quick-warp (B1) + relocate intro-skip to PlayIntro

- home/overworld.asm: SELECT in the overworld farcalls WarpMenu, then restarts
  the overworld loop so the fly-warp flags get processed.
- engine/warp_menu.asm (new): WarpMenu reuses the fly-warp machinery
  (wDestinationMap + BIT_FLY_WARP/BIT_USED_FLY). B1 warps to Pallet
  unconditionally to validate the hook; the real destination menu is next.
- Moved the fastboot intro-skip out of home/init.asm into PlayIntro (bank 10)
  to reclaim ~10 bytes of home ROM0 for the overworld hook. Net boot behavior
  is unchanged; new-game path still shows the intro.

1 files changed, 17 insertions, 0 deletions

diff --git a/engine/warp_menu.asm b/engine/warp_menu.asm
new file mode 100644
index 00000000..17cc3904
--- /dev/null
+++ b/engine/warp_menu.asm
@@ -0,0 +1,17 @@
+; Quick-warp menu, opened with SELECT in the overworld (hooked in
+; home/overworld.asm). Reuses the game's fly-warp machinery: set the
+; destination map and the fly-warp flags, then return to the overworld loop,
+; which fades out and warps us in at the destination's fly coordinates.
+
+SECTION "Warp Menu", ROMX
+
+WarpMenu::
+; B1 (pipeline validation): unconditionally warp to Pallet Town.
+	ld a, PALLET_TOWN
+	ld [wDestinationMap], a
+	ld hl, wStatusFlags6
+	set BIT_FLY_WARP, [hl]
+	ASSERT wStatusFlags6 + 1 == wStatusFlags7
+	inc hl
+	set BIT_USED_FLY, [hl]
+	ret