feat(render): Renderer with LOD selection, 3.3 and 4.3+ upload paths, headless smoke test

include/plot/gl/handle.hpp

@@ -66,6 +66,21 @@ class Buffer final : public Handle<Buffer> {
   /// Overwrites `bytes` bytes starting at `offset`; the store must already be
   /// at least `offset + bytes` large.
   void upload_sub(const void* data, usize bytes, usize offset) const noexcept;
+  /// Replaces the store with `bytes` bytes of immutable storage carrying `flags`
+  /// (`GL_MAP_WRITE_BIT` and friends). GL 4.4 / ARB_buffer_storage: only legal on
+  /// a context whose caps() report `buffer_storage`, and the entry point may be
+  /// null even on such a context (it is resolved best-effort, see api.hpp), so a
+  /// caller checks `glBufferStorage != nullptr` first. The contents start
+  /// undefined.
+  void storage(usize bytes, GLbitfield flags) const noexcept;
+
+  /// Maps `bytes` bytes from `offset` with `access`, returning the pointer or
+  /// null. GL 3.0 core, but a `GL_MAP_PERSISTENT_BIT` map needs the same
+  /// capability as `storage()` above.
+  void* map_range(usize offset, usize bytes, GLbitfield access) const noexcept;
+
+  /// Unmaps the store's data; the pointer from map_range() is invalid after this.
+  bool unmap() const noexcept;
 
   /// Exposed for the CRTP base. Deleting an unknown name is a GL no-op.
   static void destroy(GLuint id) noexcept;