Merge upstream/main into belt/rebase/may-18

Reconciles the belt-printer branch with upstream PRs through #13723. Six
files had conflicts; three additional files needed manual follow-up fixes
where the auto-merge produced code that referenced upstream-renamed fields
or changed function signatures.

Notable reconciliations:
- TreeSupport.cpp: kept belt-floor early-exit branches around HEAD's
  drop-down logic, folded upstream's `(distance_to_top > 0 ? 1 : 0)`
  formula into the non-belt-floor path (upstream PR #11812). Dropped dead
  `roof_enabled`/`force_tip_to_roof` locals.
- TreeSupport3D.cpp: combined upstream's safety-offset + remove_small
  changes with HEAD's belt-floor clip in the per-slice trim loop. Dropped
  HEAD's `else` block (superseded by upstream's rewritten bottom-contact
  propagation) and re-added the belt-floor clip into the new propagation
  loop. Gated the propagation on belt printers to prevent OOM when
  belt-floor clipping produces empty initial slices.
- TriangleSelector.{cpp,hpp}: merged both new `select_patch` parameters
  (HEAD's `up_direction` and upstream's `select_partially`); body uses
  `dot(up_direction)` for the overhang angle check and forwards
  `select_partially` to `select_triangle`.
- SupportMaterial.cpp: `slicing_params.soluble_interface` →
  `zero_gap_interface_bottom` in HEAD's `detect_belt_floor_bottom_contacts`,
  matching upstream's same-purpose rename at line 2495.
- Custom.json, GCodeWriter.cpp: simple additive merges (kept entries /
  includes from both sides).

Verified by building OrcaSlicer (RelWithDebInfo) after a full deps
rebuild (Eigen v5.0.1, libigl v2.6.0 are now managed deps) and slicing
a scaled Benchy on the NORMALIZER belt-printer profile without OOM.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

resources/shaders/110/fxaa.fs

@@ -0,0 +1,50 @@
+#version 110
+
+uniform sampler2D uniform_texture;
+uniform vec2 inv_tex_size;
+
+varying vec2 tex_coord;
+
+void main()
+{
+    vec3 rgbNW = texture2D(uniform_texture, tex_coord + vec2(-1.0, -1.0) * inv_tex_size).rgb;
+    vec3 rgbNE = texture2D(uniform_texture, tex_coord + vec2(1.0, -1.0) * inv_tex_size).rgb;
+    vec3 rgbSW = texture2D(uniform_texture, tex_coord + vec2(-1.0, 1.0) * inv_tex_size).rgb;
+    vec3 rgbSE = texture2D(uniform_texture, tex_coord + vec2(1.0, 1.0) * inv_tex_size).rgb;
+    vec3 rgbM  = texture2D(uniform_texture, tex_coord).rgb;
+
+    vec3 luma_coeff = vec3(0.299, 0.587, 0.114);
+    float lumaNW = dot(rgbNW, luma_coeff);
+    float lumaNE = dot(rgbNE, luma_coeff);
+    float lumaSW = dot(rgbSW, luma_coeff);
+    float lumaSE = dot(rgbSE, luma_coeff);
+    float lumaM  = dot(rgbM, luma_coeff);
+
+    float lumaMin = min(lumaM, min(min(lumaNW, lumaNE), min(lumaSW, lumaSE)));
+    float lumaMax = max(lumaM, max(max(lumaNW, lumaNE), max(lumaSW, lumaSE)));
+
+    vec2 dir;
+    dir.x = -((lumaNW + lumaNE) - (lumaSW + lumaSE));
+    dir.y = ((lumaNW + lumaSW) - (lumaNE + lumaSE));
+
+    const float FXAA_REDUCE_MIN = 1.0 / 128.0;
+    const float FXAA_REDUCE_MUL = 1.0 / 8.0;
+    const float FXAA_SPAN_MAX = 8.0;
+
+    float dirReduce = max((lumaNW + lumaNE + lumaSW + lumaSE) * (0.25 * FXAA_REDUCE_MUL), FXAA_REDUCE_MIN);
+    float rcpDirMin = 1.0 / (min(abs(dir.x), abs(dir.y)) + dirReduce);
+    dir = min(vec2(FXAA_SPAN_MAX), max(vec2(-FXAA_SPAN_MAX), dir * rcpDirMin)) * inv_tex_size;
+
+    vec3 rgbA = 0.5 * (
+        texture2D(uniform_texture, tex_coord + dir * (1.0 / 3.0 - 0.5)).rgb +
+        texture2D(uniform_texture, tex_coord + dir * (2.0 / 3.0 - 0.5)).rgb
+    );
+
+    vec3 rgbB = rgbA * 0.5 + 0.25 * (
+        texture2D(uniform_texture, tex_coord + dir * -0.5).rgb +
+        texture2D(uniform_texture, tex_coord + dir * 0.5).rgb
+    );
+
+    float lumaB = dot(rgbB, luma_coeff);
+    gl_FragColor = (lumaB < lumaMin || lumaB > lumaMax) ? vec4(rgbA, 1.0) : vec4(rgbB, 1.0);
+}

resources/shaders/110/fxaa.vs

@@ -0,0 +1,15 @@
+#version 110
+
+uniform mat4 view_model_matrix;
+uniform mat4 projection_matrix;
+
+attribute vec3 v_position;
+attribute vec2 v_tex_coord;
+
+varying vec2 tex_coord;
+
+void main()
+{
+    tex_coord = v_tex_coord;
+    gl_Position = projection_matrix * view_model_matrix * vec4(v_position, 1.0);
+}

resources/shaders/140/fxaa.fs

@@ -0,0 +1,52 @@
+#version 140
+
+uniform sampler2D uniform_texture;
+uniform vec2 inv_tex_size;
+
+in vec2 tex_coord;
+
+out vec4 out_color;
+
+void main()
+{
+    vec3 rgbNW = texture(uniform_texture, tex_coord + vec2(-1.0, -1.0) * inv_tex_size).rgb;
+    vec3 rgbNE = texture(uniform_texture, tex_coord + vec2(1.0, -1.0) * inv_tex_size).rgb;
+    vec3 rgbSW = texture(uniform_texture, tex_coord + vec2(-1.0, 1.0) * inv_tex_size).rgb;
+    vec3 rgbSE = texture(uniform_texture, tex_coord + vec2(1.0, 1.0) * inv_tex_size).rgb;
+    vec3 rgbM  = texture(uniform_texture, tex_coord).rgb;
+
+    vec3 luma_coeff = vec3(0.299, 0.587, 0.114);
+    float lumaNW = dot(rgbNW, luma_coeff);
+    float lumaNE = dot(rgbNE, luma_coeff);
+    float lumaSW = dot(rgbSW, luma_coeff);
+    float lumaSE = dot(rgbSE, luma_coeff);
+    float lumaM  = dot(rgbM, luma_coeff);
+
+    float lumaMin = min(lumaM, min(min(lumaNW, lumaNE), min(lumaSW, lumaSE)));
+    float lumaMax = max(lumaM, max(max(lumaNW, lumaNE), max(lumaSW, lumaSE)));
+
+    vec2 dir;
+    dir.x = -((lumaNW + lumaNE) - (lumaSW + lumaSE));
+    dir.y = ((lumaNW + lumaSW) - (lumaNE + lumaSE));
+
+    const float FXAA_REDUCE_MIN = 1.0 / 128.0;
+    const float FXAA_REDUCE_MUL = 1.0 / 8.0;
+    const float FXAA_SPAN_MAX = 8.0;
+
+    float dirReduce = max((lumaNW + lumaNE + lumaSW + lumaSE) * (0.25 * FXAA_REDUCE_MUL), FXAA_REDUCE_MIN);
+    float rcpDirMin = 1.0 / (min(abs(dir.x), abs(dir.y)) + dirReduce);
+    dir = min(vec2(FXAA_SPAN_MAX), max(vec2(-FXAA_SPAN_MAX), dir * rcpDirMin)) * inv_tex_size;
+
+    vec3 rgbA = 0.5 * (
+        texture(uniform_texture, tex_coord + dir * (1.0 / 3.0 - 0.5)).rgb +
+        texture(uniform_texture, tex_coord + dir * (2.0 / 3.0 - 0.5)).rgb
+    );
+
+    vec3 rgbB = rgbA * 0.5 + 0.25 * (
+        texture(uniform_texture, tex_coord + dir * -0.5).rgb +
+        texture(uniform_texture, tex_coord + dir * 0.5).rgb
+    );
+
+    float lumaB = dot(rgbB, luma_coeff);
+    out_color = (lumaB < lumaMin || lumaB > lumaMax) ? vec4(rgbA, 1.0) : vec4(rgbB, 1.0);
+}

resources/shaders/140/fxaa.vs

@@ -0,0 +1,15 @@
+#version 140
+
+uniform mat4 view_model_matrix;
+uniform mat4 projection_matrix;
+
+in vec3 v_position;
+in vec2 v_tex_coord;
+
+out vec2 tex_coord;
+
+void main()
+{
+    tex_coord = v_tex_coord;
+    gl_Position = projection_matrix * view_model_matrix * vec4(v_position, 1.0);
+}