Add eight effects that throw something chaotic into the chain

Slit shift, channel split, pixel sort, corruption, shatter, warp, bit
crush and feedback: tearing bands sideways, knocking the colour planes
out of register, sorting runs of pixels, damaging blocks the way a broken
stream does, breaking the picture into shards, pushing it along a noise
field, mangling its bytes and laying it over itself again and again.

All eight are pure transforms. None needs sources, so any of them can
lead a chain, and like blur they start from a crop of a random source
when they do and photographs are loaded. canvasFromSources holds that
start once for them.

Each draws its whole plan from the rng before touching a pixel, and
pixel sort hands every line a seed of its own, so the parallel work
never decides anything. The rotations in shatter and feedback take their
sine and cosine from a short series of plain multiplications rather than
libm, so a seed lands on the same pixels whatever the machine's maths
library makes of std::sin.

The tests hold every one of them to the same things -- a seed
reproduces it, it runs without sources and as a later stage, a sliver
of a canvas does not trip it, turned right down it leaves its input
alone -- plus a check of what each actually does, and the registry now
checks that no two effects declare the same param key.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

CMakeLists.txt

@@ -32,13 +32,21 @@ add_library(effector_core STATIC
     src/core/registry.cpp
     src/core/rng.cpp
     src/core/style.cpp
+    src/effects/bitcrush.cpp
     src/effects/blur.cpp
+    src/effects/channelsplit.cpp
+    src/effects/corrupt.cpp
+    src/effects/feedback.cpp
     src/effects/grain.cpp
     src/effects/monochrome.cpp
     src/effects/overlay.cpp
+    src/effects/pixelsort.cpp
     src/effects/scanlines.cpp
+    src/effects/shatter.cpp
+    src/effects/slitshift.cpp
     src/effects/text.cpp
     src/effects/tiles.cpp
+    src/effects/warp.cpp
 )
 target_include_directories(effector_core PUBLIC src)
 # The core is GUI-free: it only needs gdk-pixbuf for decoding and encoding,