[Fix, Test] (MG_Backend/DirectGLES, MG_Util, MG_Impl): widen three-channel render targets wherever the driver refuses them

Complementary Reimagined would not load through Espryt on Mali: Iris got
GL_FRAMEBUFFER_UNSUPPORTED building its composite framebuffer, because
colortex1 is RGB8_SNORM and colortex2 is RGB16F - three-channel formats
that no real ES driver can render to (EXT_render_snorm covers R/RG/RGBA
only, and the float extensions exclude the RGB forms). The frontend's
probe cache diagnosed this correctly and then had nothing to offer: the
NoThreeChannelRenderTarget widening machinery existed but was gated to
multisample targets alone. llvmpipe turns out to refuse most of the same
attachments - CI retrace stayed green only because a replay never
branches on glCheckFramebufferStatus - so this was never a desktop-vs-
device split, just an unlit path.

The widening now applies to every color-attachable image, renderbuffers
included, riding the driver-probe branch so the native format is still
tried first and substituted only on refusal. One ThreeChannelWidening
table owns the widened (internalformat, format, type) triple per source
format - the previous per-case branches disagreed with each other and
could emit an unuploadable (RGBA16F, GL_RGB, GL_BYTE) combination or
widen into another three-channel format the driver refuses just the
same. Uploads repack three-component client data to four with the
format's own one in the alpha channel (127 is not 1 for RGB8I - the
integer arms carry integer ones); readback drops the synthetic alpha,
derived from the actual image being read, not the bound framebuffer,
so glGetTexImage through a scratch FBO cannot be confused by an
unrelated widened attachment.

Stored alpha on a widened attachment is now an invariant 1.0 rather
than an accident: the color-mask sync clears the alpha bit per draw
buffer (glColorMaski for MRT mixes), and clears route through
glClearBufferfv with alpha substituted on widened slots only -
scissored clears inherit the discipline for free, integer color
buffers keep their explicit integer-clear path, and glGet still
answers the application's own mask. GL_DST_ALPHA blending, blits and
readback therefore all see 1.0 without further interception.

DriverPost grows the rows this bug earned: EXT_color_buffer_float
detection (previously unreferenced anywhere) with a FAIL row when
absent, the missing EXT_render_snorm row, and a three-channel-
attachment row that reports one representative per widening class -
graded so a half-float-only driver warns about the 32-bit float gap
instead of being declared unsupported.

Gates: 606/606 unit at default and with the async kill switch; full
retrace, both backends - the complementary fixtures now run with the
widening ACTIVE on llvmpipe and pass with a slightly better SSIM than
before; ext caselist DirectGLES holds 3914/4867 with zero set drift
while 54 cases move from NotSupported to genuinely passing; on the
Mali-G77 device, Complementary Reimagined builds its pipeline and
renders in-world through Espryt (md5-verified build), BSL still green.
A new ThreeChannelAttachmentScenario pins the frontend answer -
COMPLETE where it used to say UNSUPPORTED - on the real driver.

MobileGL/MG_Backend/DirectGLES/DirectGLES.h

@@ -188,6 +188,26 @@ namespace MobileGL::MG_Backend::DirectGLES {
         void OnBackendContextDestroyed();
     } // namespace XfbImpl
 
+    namespace RenderStateImpl {
+        // Pushes the frontend's render-state block to the ES driver, diffed against what was
+        // last pushed.
+        //
+        // `forColorClear` names the CALLER, and the only thing it changes is the colour write
+        // mask handed to the driver. A draw into a colour attachment the backend widened from
+        // three channels to four gets that buffer's alpha channel masked OFF, so nothing can
+        // move the stored alpha away from the 1.0 the application's three-channel format
+        // implies (see FramebufferImpl::g_alphaWidenedDrawBufferMask). A CLEAR is how that 1.0
+        // gets there in the first place, so it must be allowed to write alpha - hence the flag
+        // rather than an unconditional doctoring. It is part of the sync memo, so a clear
+        // followed by a draw re-pushes the mask instead of early-outing on an unchanged
+        // frontend version.
+        //
+        // The application's own colour mask is never modified: glGet(GL_COLOR_WRITEMASK)
+        // answers from the frontend state, which this function only reads.
+        void SyncRenderState(Bool forColorClear = false);
+        void InvalidateSyncedRenderState();
+    } // namespace RenderStateImpl
+
     extern MG_External::EGLFunctionsTable g_EGLFuncs;
     extern MG_External::GLESFunctionsTable g_GLESFuncs;
     extern MG_External::GLESCapabilities g_GLESCapabilities;