feat(shaders_lab): uniform annotations → auto-generated ImGui controls

- cpp/functions/gfx/uniform_parser: regex-based parser of @slider/@color/@toggle/@xy annotations (+ inline tests)
- cpp/functions/gfx/uniform_panel: ImGui widgets + value store + glUniform* apply
- shader_canvas: optional uniforms callback invoked per-frame
- gl_loader: +glUniform1i/3f/4f
- seed plasma: demo uniforms u_speed + u_color
- rebuild Windows .exe

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

cpp/apps/shaders_lab/CMakeLists.txt

@@ -5,6 +5,8 @@ add_imgui_app(shaders_lab
     ${CMAKE_SOURCE_DIR}/functions/gfx/gl_framebuffer.cpp
     ${CMAKE_SOURCE_DIR}/functions/gfx/fullscreen_quad.cpp
     ${CMAKE_SOURCE_DIR}/functions/gfx/shader_canvas.cpp
+    ${CMAKE_SOURCE_DIR}/functions/gfx/uniform_parser.cpp
+    ${CMAKE_SOURCE_DIR}/functions/gfx/uniform_panel.cpp
     ${CMAKE_SOURCE_DIR}/functions/core/fps_overlay.cpp
 )
 target_include_directories(shaders_lab PRIVATE

cpp/apps/shaders_lab/main.cpp

@@ -3,11 +3,14 @@
 
 #include "gfx/shader_canvas.h"
 #include "gfx/gl_shader.h"
+#include "gfx/uniform_parser.h"
+#include "gfx/uniform_panel.h"
 #include "core/fps_overlay.h"
 #include "seed_shaders.h"
 
 #include <chrono>
 #include <string>
+#include <vector>
 
 static fn::gfx::ShaderCanvas g_canvas;
 static std::string g_source = PLASMA;
@@ -15,10 +18,14 @@ static std::string g_last_err;
 static int g_last_err_line = -1;
 static std::chrono::steady_clock::time_point g_last_edit;
 static bool g_dirty = true;
+static std::vector<fn::gfx::UniformDescriptor> g_descs;
+static fn::gfx::UniformStore g_store;
 
 static void try_compile() {
     auto r = fn::gfx::compile_fragment(g_source);
     if (r.ok) {
+        g_descs = fn::gfx::parse_uniforms(g_source);
+        fn::gfx::uniforms_sync(g_store, g_descs);
         fn::gfx::canvas_set_program(g_canvas, r.program);
         g_last_err.clear();
         g_last_err_line = -1;
@@ -91,13 +98,16 @@ static void render() {
 
     // --- Canvas panel ---
     if (ImGui::Begin("Canvas")) {
-        fn::gfx::canvas_render(g_canvas, static_cast<float>(ImGui::GetTime()));
+        fn::gfx::canvas_render(g_canvas, static_cast<float>(ImGui::GetTime()),
+            [](unsigned int program) {
+                fn::gfx::uniforms_apply(g_store, g_descs, program);
+            });
     }
     ImGui::End();
 
     // --- Controls panel ---
     if (ImGui::Begin("Controls")) {
-        ImGui::TextDisabled("Controls (fase 2)");
+        fn::gfx::uniforms_panel(g_store, g_descs);
         ImGui::Spacing();
         fps_overlay();
     }

cpp/apps/shaders_lab/seed_shaders.h

@@ -4,24 +4,14 @@
 // compile_fragment() prepends those automatically.
 
 static const char* PLASMA = R"glsl(
+uniform float u_speed;   // @slider min=0.1 max=5 default=1
+uniform vec3  u_color;   // @color default=0.5,0.2,0.8
+
 void main() {
     vec2 uv = gl_FragCoord.xy / u_resolution;
-    float t = u_time * 0.5;
-
-    float v1 = sin(uv.x * 10.0 + t);
-    float v2 = sin(uv.y * 10.0 + t * 1.3);
-    float v3 = sin((uv.x + uv.y) * 10.0 + t * 0.7);
-    float v4 = sin(length(uv - 0.5) * 20.0 - t * 2.0);
-
-    float v = (v1 + v2 + v3 + v4) * 0.25;
-
-    vec3 col = vec3(
-        sin(v * 3.14159 + 0.0) * 0.5 + 0.5,
-        sin(v * 3.14159 + 2.094) * 0.5 + 0.5,
-        sin(v * 3.14159 + 4.188) * 0.5 + 0.5
-    );
-
-    fragColor = vec4(col, 1.0);
+    float t = u_time * u_speed;
+    vec3 c = u_color * (0.5 + 0.5 * cos(t + uv.xyx + vec3(0.0, 2.0, 4.0)));
+    fragColor = vec4(c, 1.0);
 }
 )glsl";