Revert the MSAA resolve-depth attachment changes

SDL_gpu cannot sample a multisample texture, so the sampleable multisampled
depth and its single-sample resolve target could never work. The consuming
application instead writes a single-sample float depth copy to a color
attachment (which does resolve), so these changes are unnecessary. Reverts to
the resolveColorTexture / single-sample sampleable-depth baseline.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: jdolan

Sources/ObjectivelyGPU/Framebuffer.c

@@ -183,34 +183,20 @@ static bool resize(Framebuffer *self, const SDL_Size *size) {
 
   if (self->depthFormat != SDL_GPU_TEXTUREFORMAT_INVALID) {
 
-    // Depth carries SAMPLER so it can be read in a shader. Single-sample depth is
-    // read directly via resolveDepthTexture (e.g. soft particles). Multisampled
-    // depth is read (as a multisample texture) by an app resolve pass that writes
-    // the separate single-sample resolveDepthTexture, since SDL has no depth
-    // store-op resolve.
+    // Single-sample depth carries SAMPLER so it can be read directly via
+    // resolveDepthTexture (e.g. soft particles). Multisampled depth is a plain
+    // depth-stencil target; sampling it requires the separate resolveDepthTexture,
+    // populated by a resolve pass (SDL has no depth store-op resolve) — TODO when MSAA lands.
     self->depthTexture = $(self->device, createTexture, &(SDL_GPUTextureCreateInfo) {
       .type = SDL_GPU_TEXTURETYPE_2D,
       .format = self->depthFormat,
-      .usage = SDL_GPU_TEXTUREUSAGE_DEPTH_STENCIL_TARGET | SDL_GPU_TEXTUREUSAGE_SAMPLER,
+      .usage = SDL_GPU_TEXTUREUSAGE_DEPTH_STENCIL_TARGET | (multisampled ? 0 : SDL_GPU_TEXTUREUSAGE_SAMPLER),
       .width = (Uint32) self->size.w,
       .height = (Uint32) self->size.h,
       .layer_count_or_depth = 1,
       .num_levels = 1,
       .sample_count = self->sampleCount,
     }, NULL);
-
-    if (multisampled) {
-      self->resolveDepthTexture = $(self->device, createTexture, &(SDL_GPUTextureCreateInfo) {
-        .type = SDL_GPU_TEXTURETYPE_2D,
-        .format = self->depthFormat,
-        .usage = SDL_GPU_TEXTUREUSAGE_DEPTH_STENCIL_TARGET | SDL_GPU_TEXTUREUSAGE_SAMPLER,
-        .width = (Uint32) self->size.w,
-        .height = (Uint32) self->size.h,
-        .layer_count_or_depth = 1,
-        .num_levels = 1,
-        .sample_count = SDL_GPU_SAMPLECOUNT_1,
-      }, NULL);
-    }
   }
 
   return true;