feat(shaders_lab): DAG pipeline mode with node catalog

- cpp/functions/gfx/dag_types: DagStep, DagNodeDef, DagControl (header-only)
- cpp/functions/gfx/dag_catalog: 10 hardcoded nodes (4 gen, 3 op, 3 blend) ported from shader-dag-blends.jsx
- cpp/functions/gfx/dag_compile: pipeline → GLSL 330 core with fan-in via source_id
- cpp/functions/gfx/dag_uniforms: upload u_params[16] via glUniform4fv
- cpp/functions/gfx/dag_panel: ImGui pipeline editor (add/remove/reorder/controls)
- main.cpp: Code/DAG mode toggle, per-mode compile path and uniforms
- gl_loader: +glUniform4fv
- rebuild Windows .exe

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

types/gfx/dag_types.md

@@ -0,0 +1,45 @@
+---
+name: dag_types
+lang: cpp
+domain: gfx
+version: "1.0.0"
+algebraic: product
+definition: |
+  enum class DagKind { Gen, Op, Blend };
+
+  struct DagControl {
+      enum class Kind { Slider, XY, Color };
+      Kind kind;
+      std::string label;
+      std::array<int, 3> param_idx{-1, -1, -1};
+      float min = 0.0f;
+      float max = 1.0f;
+      float step = 0.0f;
+  };
+
+  struct DagNodeDef {
+      std::string name;
+      std::string label;
+      std::string desc;
+      DagKind kind = DagKind::Gen;
+      std::array<std::string, 4> param_names{"", "", "", ""};
+      std::array<float, 4> param_defaults{0, 0, 0, 0};
+      std::vector<DagControl> controls;
+      std::function<std::string(int idx)> body_glsl;
+  };
+
+  struct DagStep {
+      std::string id;
+      std::string name;
+      std::array<float, 4> params{0, 0, 0, 0};
+      std::string source_id;
+  };
+description: "Tipos del DAG de shaders: DagKind (gen/op/blend), DagControl (descriptor de widget UI), DagNodeDef (entrada del catalogo de nodos con body GLSL), DagStep (paso del pipeline con params y source_id estable ante reorders)."
+tags: [dag, shader, gfx, pipeline, nodes, types]
+uses_types: []
+file_path: "cpp/functions/gfx/dag_types.h"
+---
+
+## Notas
+
+Header-only. DagNodeDef::body_glsl es un callable que recibe el indice del nodo en el pipeline y devuelve el cuerpo GLSL de la funcion (sin llaves). DagStep::source_id es el id estable del paso fuente para blends; sobrevive a reordenamientos del pipeline porque referencia por id, no por indice.