feat(jobs): sistema de jobs asincronos + panel UI (issue 0026)

Infra para correr enrichers en background mientras la app sigue interactiva.

C++:
- jobs.{h,cpp}: tabla jobs en graph_explorer.db, JobRunner con N=2 std::thread
  workers, fork+exec POSIX con pipes, parser de PROGRESS:<float> <stage> en
  stderr, captura de stdout JSON, persistencia + dirty_counter.
- enrichers.{h,cpp}: scanner de enrichers/<id>/manifest.yaml, parser YAML
  minimo (id/name/description/applies_to), filtro por tipo de nodo.
- views_jobs.cpp: panel "Jobs" dockeable con tabla (status/enricher/target/
  progress/time), filtro all/active/done/errors, cancelar/borrar inline.

Wiring:
- main.cpp: resolve_registry_root() (FN_REGISTRY_ROOT env o subir desde cwd
  buscando registry.db), jobs_init/enrichers_load antes de fn::run_app,
  jobs_shutdown al cerrar, dirty_counter -> want_reload, jobs_set_ops_db al
  cambiar de proyecto.
- main.cpp:render_context_menu: menu "Run enricher" sustituye placeholder
  con submenu filtrado por type_ref via enrichers_for_type. Submit abre
  panel Jobs auto.
- views.h: AppState::panel_jobs flag + decl views_jobs().
- CMakeLists.txt: anade jobs.cpp + enrichers.cpp + views_jobs.cpp y enlaza
  Threads::Threads.

Wire protocol enricher (subprocess Python):
- stdin:  JSON con node_id, metadata, ops_db_path, app_dir, cache_dir,
          registry_root, params.
- stderr: PROGRESS:<float> <stage> + LOG lineas libres.
- stdout: JSON resumen al final.
- exit 0 = ok, !=0 = error con stderr capturado en panel Jobs.

El run.py escribe directamente al operations.db (sqlite3 stdlib) — C++ solo
orquesta, no parsea entities/relations.

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

CMakeLists.txt

@@ -18,11 +18,14 @@ add_imgui_app(graph_explorer
     main.cpp
     data.cpp
     views.cpp
+    views_jobs.cpp
     types_registry.cpp
     layout_store.cpp
     entity_ops.cpp
     project_manager.cpp
     tableview.cpp
+    jobs.cpp
+    enrichers.cpp
     # --- viz ---
     ${FN_CPP_ROOT_DIR}/functions/viz/graph_renderer.cpp
     ${FN_CPP_ROOT_DIR}/functions/viz/graph_force_layout.cpp
@@ -58,6 +61,10 @@ target_include_directories(graph_explorer PRIVATE
 target_link_libraries(graph_explorer PRIVATE SQLite::SQLite3 DuckDB::DuckDB)
 duckdb_copy_runtime(graph_explorer)
 
+# Threads — issue 0026 (jobs system) usa std::thread + std::mutex + condvar.
+find_package(Threads REQUIRED)
+target_link_libraries(graph_explorer PRIVATE Threads::Threads)
+
 # OpenGL: graph_renderer + graph_force_layout_gpu llaman gl* directamente.
 # fn::run_app inicializa el loader cuando AppConfig::init_gl_loader = true.
 if(NOT WIN32)