chore(issues): plan 0049 OSINT graph viewer multi-issue

Aggregates the planning artifacts for the 0049 series (umbrella + 0049a..0049k):

- New rule cpp_apps.md (registered in INDEX) — standardize structure, CMake
  patterns, app.md frontmatter and sub-repo for C++ apps; points to the
  authoritative cpp/PATTERNS.md and cpp/DESIGN_SYSTEM.md.
- Feature flag osint_graph_v1 (disabled until 0049k closes).
- Issue 0049 (umbrella) and sub-issues 0049b..0049k describing the GPU
  rendering system, force-layout, types, sources, labels and the final
  graph_explorer app integration.
- README updated with the new rows (all pending; 0049a will flip to
  completed in the next commit).

dev/feature_flags.json

@@ -3,5 +3,11 @@
     "enabled": true,
     "issue": "0007",
     "description": "Sistema propio de orquestacion de DAGs para reemplazar Dagu. Incluye parser YAML, executor con paralelismo, process manager, execution store SQLite, scheduler cron, CLI y web frontend."
+  },
+  "osint_graph_v1": {
+    "enabled": false,
+    "issue": "0049",
+    "description": "Visor de grafos GPU-accelerated agnostico del backend (graph_explorer en projects/osint_graph) + sistema de renderer extendido (shapes, iconos Tabler, edge styles, flechas, layouts force-GPU/radial/hierarchical, labels con politica). Activado al cerrar 0049k.",
+    "added": "2026-04-29"
   }
 }