Replace per-node text capture with camera-distance ring multi-pass

The previous nearest-first build captured every deferred visual node as text into a
sorted vector, which does not scale: one tomaszewo flora file alone holds 440k model
nodes (the scenery has 1M+), so the capture ran the process to ~7 GB and its
enumeration never finished.

Stream the visual nodes in camera-distance rings instead, with no per-node capture
(O(1) memory). The visual pass replays the twin once per ring (nearest first); a node
is built only when its squared distance to the camera -- sampled once when the visual
phase starts, so the partition is stable across passes -- falls in the current ring,
otherwise the rest of its body is skipped in O(1) by jumping over the v6 marker span.
Each node is therefore built exactly once, in roughly nearest-first order, through the
normal node path (instancing buckets unchanged). Explicit triangles/lines shapes have
no single position to ring-test by, so they build in the nearest ring pass only.

Reader gains skip_to_node_end() (remembers the served node's end and jumps the cursor
there); cParser::skipReplayNode() delegates it down the active include child.

Verified: td.scn builds 4 rings, no duplicates, no unexpected tokens, complete ~1s
after the infrastructure pass. tomaszewo stays memory-bounded (no OOM, no duplicates)
where the capture approach previously hung.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

scene/scenerybinary.h

@@ -148,6 +148,11 @@ public:
     // decodes the next served entry into Out, skipping node markers / out-of-pass nodes;
     // returns false once all entries are consumed
     bool next( scenery_entry_view &Out );
+    // jumps the cursor to the end of the node currently being served, so the rest of its
+    // body is skipped in O(1). valid right after next() handed out an entry belonging to a
+    // node; returns false (no-op) otherwise. used by the camera-ring visual load to drop a
+    // node outside the current distance ring once its position has been read.
+    bool skip_to_node_end() { if( m_nodeend == nullptr ) { return false; } m_cursor = m_nodeend; m_nodeend = nullptr; return true; }
     bool exhausted() const { return m_cursor >= m_end; }
     // fraction of bytes consumed so far, 0..100, for the loading bar
     int progress() const { return ( m_size == 0 ? 100 : static_cast<int>( ( m_cursor - m_begin ) * 100 / m_size ) ); }
@@ -157,6 +162,7 @@ private:
     char const *m_begin { nullptr }; // start of the entry section
     char const *m_cursor { nullptr };
     char const *m_end { nullptr };
+    char const *m_nodeend { nullptr }; // end of the node currently being served (for skip_to_node_end)
     std::ptrdiff_t m_size { 0 };      // entry section byte length
     scenery_load_pass m_pass { scenery_load_pass::all };
     scenery_file_kind m_kind { scenery_file_kind::scn };