docs(capabilities): unifica tag gamedev en gamedev-2d + separa gamedev-engine

El doctor reportaba el dominio gamedev en doble FAIL: el tag plano `gamedev`
(44 funciones) como `ungrouped_candidate` y la pagina `gamedev-2d.md` como
`doc_orphan`. Causa raiz: el INDEX declaraba `[gamedev](gamedev-2d.md)` y el
auditor solo registra el slug cuando label==target, asi que ni casaba la
pagina ni declaraba el tag.

Al revisar las 44 funciones habia dos clusters reales bajo el mismo tag, asi
que se separan en dos grupos honestos:

- gamedev-2d (tag canonico): 31 builders de workflow ComfyUI + 5 de apoyo
  (post-proceso + puente a Godot) = 36. Se elimina el tag plano `gamedev` de
  los builders (ya tenian `gamedev-2d`) y se reemplaza por `gamedev-2d` en las
  de apoyo.
- gamedev-engine (grupo nuevo, pagina madre nueva): runtime de juego C++
  multiplataforma (SDL3 + sokol_gfx + miniaudio, Issue 0072b) = 8. Game loop,
  camara 2D, input unificado, sprite batch, setup render/audio, build wasm.

El tag plano `gamedev` queda eliminado (count 0). INDEX corregido: fila
gamedev-2d con label==target y conteo 36 + fila nueva gamedev-engine (8).

Verificacion: `fn index` + `fn doctor capabilities` -> ambos grupos OK
(declared_in_index=yes, doc_exists=yes, sin issues); `gamedev` plano = 0.
Solo se modifico el campo `tags` de los .md, ningun archivo de codigo.

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

cpp/functions/gamedev/audio_engine.md

@@ -7,7 +7,7 @@ version: "0.1.0"
 purity: impure
 signature: "engine_init() -> Engine; engine_shutdown(Engine&); engine_set_volume(Engine&, float)"
 description: "Lifecycle del engine de audio basado en miniaudio (single-header, public domain). Inicializa device default, expone master volume, y libera recursos. Cross-platform: Windows/Linux/macOS via WASAPI/ALSA/CoreAudio y WebAudio bajo emscripten. Issue 0072b — runtime gamedev nucleo. Esta TU es la unica del proyecto que define MINIAUDIO_IMPLEMENTATION."
-tags: [gamedev, audio, miniaudio]
+tags: [gamedev-engine, audio, miniaudio]
 uses_functions: []
 uses_types: []
 returns: []

cpp/functions/gamedev/audio_play.md

@@ -7,7 +7,7 @@ version: "0.1.0"
 purity: impure
 signature: "sound_load(Engine&, const char*) -> Sound; sound_play/stop/set_volume/destroy(Sound&); play_sound_oneshot(Engine&, const char*, float)"
 description: "Reproduccion de audio sobre fn::audio::Engine: carga sonidos con streaming desde disco (wav/mp3/flac/ogg), play/stop/volumen por sonido, y helper fire-and-forget para one-shots sin handle. Cross-platform via miniaudio. Issue 0072b — runtime gamedev nucleo."
-tags: [gamedev, audio, miniaudio]
+tags: [gamedev-engine, audio, miniaudio]
 uses_functions: ["audio_engine_cpp_gamedev"]
 uses_types: []
 returns: []

cpp/functions/gamedev/camera_2d.md

@@ -7,7 +7,7 @@ version: "0.1.0"
 purity: pure
 signature: "world_to_screen(Camera2D, Vec2) -> Vec2; screen_to_world(Camera2D, Vec2) -> Vec2; visible_world_rect(Camera2D) -> Rect; view_proj_matrix(Camera2D, float[16])"
 description: "Camara ortografica 2D pura: pos (centro), zoom, rotacion (rad) y viewport en pixeles. Conversiones world<->screen, AABB visible y matriz view-projection 4x4 column-major lista para cualquier renderer (sokol_gfx, OpenGL, WebGPU). Fast-path sin trig si rotation==0. Issue 0072b."
-tags: [gamedev, camera, 2d, math, pure]
+tags: [gamedev-engine, camera, 2d, math, pure]
 uses_functions: []
 uses_types: ["Vec2_cpp_core", "Rect_cpp_core"]
 returns: []

cpp/functions/gamedev/game_loop.md

@@ -7,7 +7,7 @@ version: "0.1.0"
 purity: impure
 signature: "loop_run(SDL_Window*, const LoopCfg&) -> void"
 description: "Game loop fixed-timestep estilo Glenn Fiedler ('Fix Your Timestep'). Desacopla simulacion (on_fixed_update con dt fijo) de renderizado (on_render con factor de interpolacion). Acumulador con cap anti spiral-of-death. Branch automatico desktop (while loop bloqueante) vs __EMSCRIPTEN__ (emscripten_set_main_loop). Issue 0072b."
-tags: [gamedev, game-loop, sdl3, wasm, fixed-timestep]
+tags: [gamedev-engine, game-loop, sdl3, wasm, fixed-timestep]
 uses_functions: []
 uses_types: []
 returns: []

cpp/functions/gamedev/input_unified.md

@@ -7,7 +7,7 @@ version: "0.1.0"
 purity: impure
 signature: "input_begin_frame(InputState&); input_process_event(InputState&, const SDL_Event*)"
 description: "Snapshot unificado de input por frame para SDL3. Mapea keyboard (WASD+arrows), mouse, gamepad (SDL_Gamepad) y touch a botones logicos (left/right/up/down/action_a..y/start/back) y ejes analogicos. Expone flags *_pressed con rising edge limpio cada frame. Issue 0072b — runtime gamedev PC + WASM."
-tags: [gamedev, input, sdl3, touch, gamepad]
+tags: [gamedev-engine, input, sdl3, touch, gamepad]
 uses_functions: []
 uses_types: []
 returns: []

cpp/functions/gfx/sokol_setup.md

@@ -7,7 +7,7 @@ version: "0.1.0"
 purity: pure
 signature: "make_environment() -> sg_environment; make_swapchain(int w, int h) -> sg_swapchain"
 description: "Builders puros para inicializar sokol_gfx encima de un GL context creado por SDL3 (no por sokol_app). Construye sg_environment con defaults RGBA8 + depth/stencil y sg_swapchain con el default framebuffer del contexto activo. Issue 0072b — base del runtime gamedev en PC + WASM."
-tags: [gamedev, sokol, gfx, sdl3, wasm]
+tags: [gamedev-engine, sokol, gfx, sdl3, wasm]
 uses_functions: []
 uses_types: []
 returns: []

cpp/functions/gfx/sprite_batch.md

@@ -7,7 +7,7 @@ version: "0.1.0"
 purity: impure
 signature: "sprite_batch_create(int cap=4096) -> SpriteBatch; sprite_batch_begin/draw/end"
 description: "Batched textured quad renderer sobre sokol_gfx. Begin/draw/end con auto-flush por atlas change o capacity full. Vertex layout pos+uv+color, alpha blending estandar, GLSL 330 / GLES 300. Issue 0072b runtime gamedev — base de plataformeros, top-down, UI sprites."
-tags: [gamedev, gfx, sokol, sprite, batch, 2d]
+tags: [gamedev-engine, gfx, sokol, sprite, batch, 2d]
 uses_functions:
   - sokol_setup_cpp_gfx
 uses_types: