Add AI-upscaled critter/object art as a new MDL mod type

Extends the MDL system beyond text overrides: bitmaps/<label>.json
names a model/scale and resource list, and mdlp extracts each
resource's frames, runs them through an ONNX Runtime CPU upscaler
baked into mdlp-image, re-quantizes to the game's palette, and writes
the result back - same build-time pipeline as message overrides.

Adds animgallery, a standalone viewer that renders any data
directory's animated resources as an HTML/GIF gallery with a
checkbox-driven MDL JSON generator, and -only-changed to preview just
what a mod overrides against the base game.

Fixes a real data race in hacked's ChangeNotifier.hashAll() (found via
go build -race causing non-deterministic resource counts), via a new
numbered patch rather than editing the vendored source.

Adds engine-patches/, a general-fixes counterpart to
android/engine-patches/ now staged and applied to the desktop builds
too (previously unpatched): a real GL_UNPACK_ROW_LENGTH stride bug, an
audio error-logging improvement, and two critter-rendering fixes -
mod art was losing to the base game's own re-opened resource files,
and critters rendered at the wrong size/position once that was fixed,
both from how the billboard renderer derives on-screen size and
placement straight from bitmap pixel dimensions.

Updates README.md and AGENTS.md to document engine-patches/.

modding/Makefile

@@ -13,8 +13,24 @@
 #   mods             - builds every mod under mods/ via that image, offline.
 #                       Set MODS="name1 name2" to build only those. Output
 #                       lands in dist/mods/.
+#   animgallery_base - browses res/assets/ss_ee/data alone: every animated
+#                       resource as a looping GIF in build/gallery-base/.
+#   animgallery_mods - same, but with every built mod under dist/mods/
+#                       layered on top (later wins), in build/gallery-mods/ -
+#                       shows what a mod actually changes without launching
+#                       the game. Run `make mods` first.
+#   animgallery_dist - every built mod under dist/mods/ layered on top of
+#                       the base game, like animgallery_mods, but restricted
+#                       to only the resources a mod actually overrides, in
+#                       build/gallery-dist/ - a focused "what did my mods
+#                       change" view, in the base game's own colors (unlike
+#                       a mod's own output alone, which has no palette
+#                       resource and would render in grayscale).
+#                       Run `make mods` first.
+#                       (animgallery_base/_mods/_dist all write into this
+#                       subproject's own build/, not the repo root's.)
 #   clean            - removes dist/.
-.PHONY: all build-image hacked mdlp-image mods clean
+.PHONY: all build-image hacked mdlp-image mods animgallery_base animgallery_mods animgallery_dist clean
 
 export MODS
 
@@ -45,5 +61,31 @@ mods:
 		./mdlp-run-image.sh; \
 	fi
 
+animgallery_base:
+	./gen_animgallery.sh -data res/assets/ss_ee/data -out modding/build/gallery-base
+
+# Layers every built mod's mod/ folder on top of the base assets, later
+# wins - same discovery pattern as res/run-mods.sh.
+animgallery_mods:
+	@ARGS="-data res/assets/ss_ee/data"; \
+	for d in dist/mods/*/mod; do \
+		[ -d "$$d" ] && ARGS="$$ARGS -data modding/$$d"; \
+	done; \
+	./gen_animgallery.sh $$ARGS -out modding/build/gallery-mods
+
+# Same layering as animgallery_mods, but -only-changed restricts the output
+# to resources a mod layer actually overrides.
+animgallery_dist:
+	@ARGS="-data res/assets/ss_ee/data"; \
+	FOUND=""; \
+	for d in dist/mods/*/mod; do \
+		[ -d "$$d" ] && ARGS="$$ARGS -data modding/$$d" && FOUND=1; \
+	done; \
+	if [ -z "$$FOUND" ]; then \
+		echo "PREFLIGHT FAIL: no built mods found under dist/mods/ - run 'make mods' first" >&2; \
+		exit 1; \
+	fi; \
+	./gen_animgallery.sh $$ARGS -only-changed -out modding/build/gallery-dist
+
 clean:
 	rm -rf dist