feat: graph_explorer app — agnostic operations.db viewer (issue 0049k)

App C++ ImGui que abre cualquier operations.db del registry y lo visualiza
como grafo con shapes/iconos/layouts/filtros/labels.

Composicion del registry:
- viz/graph_renderer + graph_force_layout(_gpu) + graph_layouts +
  graph_viewport + graph_labels + graph_icons + graph_sources
- core: toolbar, modal_dialog, select, text_input, tree_view, page_header,
  fullscreen_window, button, badge, empty_state

Capas:
- data.{h,cpp}    — dispatcher GraphLoadFn (operations hoy; json/graphml manana).
- types_registry.{h,cpp} — parser YAML minimal + tabler_codepoint_by_name +
  apply_types_yaml + IconAtlas builder.
- views.{h,cpp}   — Toolbar, Legend, Inspector, Stats, modal Filters/Open.
- layout_store.{h,cpp} — graph_explorer.db SQLite con tabla layouts(graph_hash,
  node_id, x, y, pinned, updated_at). UPSERT por nodo.
- main.cpp        — CLI (--input/--types/--layout) + fn::run_app + bucle
  force layout (CPU/GPU toggle) + render con 3 columnas (Legend / Viewport /
  Inspector+Stats).

examples/types.yaml: 10 entidades OSINT (Person/Email/Domain/Phone/Org/IBAN/
Account/Document/Address/Url) + 5 relaciones (owns/knows/located_in/
transfers_to/member_of) con shapes Tabler reales.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

app.md

@@ -0,0 +1,80 @@
+---
+name: graph_explorer
+lang: cpp
+domain: viz
+description: "Visor de grafos GPU-accelerated agnostico del backend. Lee operations.db de cualquier app del registry y permite explorar entidades/relaciones con shapes/iconos/layouts/filtros."
+tags: [imgui, graph, osint, visualization, gpu]
+uses_functions:
+  - graph_renderer_cpp_viz
+  - graph_force_layout_cpp_viz
+  - graph_force_layout_gpu_cpp_viz
+  - graph_layouts_cpp_viz
+  - graph_viewport_cpp_viz
+  - graph_labels_cpp_viz
+  - graph_icons_cpp_viz
+  - graph_sources_cpp_viz
+  - toolbar_cpp_core
+  - modal_dialog_cpp_core
+  - select_cpp_core
+  - text_input_cpp_core
+  - tree_view_cpp_core
+  - page_header_cpp_core
+  - fullscreen_window_cpp_core
+uses_types: []
+framework: "imgui"
+entry_point: "main.cpp"
+dir_path: "projects/osint_graph/apps/graph_explorer"
+repo_url: "https://gitea-dgg044oo04woo4ggcsws4gk0.organic-machine.com/dataforge/graph_explorer"
+---
+
+## Arquitectura
+
+App C++ ImGui para explorar cualquier `operations.db` del registry como un grafo
+de entidades y relaciones. Agnostica del backend — el dispatcher en
+`data.{h,cpp}` selecciona el `GraphLoadFn` segun `--input` (hoy solo
+`operations`, manana `json`/`jsonl`/`graphml`).
+
+**Capas:**
+
+- `data.{h,cpp}` — dispatcher de sources. Hoy unica implementacion:
+  `graph_load_from_operations` (issue 0049g).
+- `types_registry.{h,cpp}` — parser minimo de YAML para sobrescribir
+  `color`/`shape`/`icon`/`style` por nombre de tipo. Construye el `IconAtlas`
+  con los codepoints Tabler resueltos por `tabler_codepoint_by_name`.
+- `views.{h,cpp}` — paneles `Toolbar`, `Legend`, `Inspector`, `Stats`. Toggle
+  via `AppConfig::panels`.
+- `main.cpp` — CLI + `fn::run_app` + bucle de force layout (CPU/GPU) + glue.
+- `graph_explorer.db` — SQLite junto al exe. Tabla `layouts(graph_hash,
+  node_id, x, y, pinned, updated_at)`. Persistencia de posiciones por grafo.
+
+## CLI
+
+```bash
+graph_explorer [<operations.db>]
+graph_explorer --input operations <path>
+graph_explorer --types <yaml>
+graph_explorer --layout force|grid|circular|radial|hierarchical|fixed
+graph_explorer apps/registry_dashboard/operations.db
+graph_explorer --types projects/osint_graph/apps/graph_explorer/examples/types.yaml \
+               apps/element_agents/operations.db
+```
+
+## Build
+
+```bash
+cd cpp
+cmake -B build/linux -S .
+cmake --build build/linux --target graph_explorer -j$(nproc)
+./build/linux/apps/graph_explorer/graph_explorer apps/registry_dashboard/operations.db
+```
+
+## Notas
+
+- Usa GPU layout si el contexto soporta compute 4.3; toggle CPU/GPU desde la
+  toolbar. Fallback transparente a CPU si GPU no esta disponible.
+- 50k nodos a 60fps con layout GPU (medido en demos/graph en
+  `primitives_gallery`).
+- `operations.db` se abre con `mode=ro` cuando el path no apunta al
+  filesystem propio para evitar lock con otras apps que esten escribiendo.
+- El `graph_hash` se calcula a partir del path canonico del input. Mismo path
+  = mismo grafo a efectos de layout guardado.