Add headless parallel eu7v2 scenario bake with streaming and PLCE placements

Enable --eu7v2-bake from the main binary: parallel module pool, bounded-RAM
spool flush, streaming terrain triangles, flat include/model parsing, and
eu7v2 emit/load with optional verify. Large placement .scm files emit lean
PLCE records and bake referenced .inc modules separately for reuse.

- CLI: --eu7v2-bake, --eu7v2-verify, --eu7v2-mem-limit-gb, --eu7v2-threads,
  --eu7v2-max-parse; wire max_threads through to the bake parser
- eu7v2 v2 records: PLCE placements, runtime emitter/loader, batch verify
- Parallel bake pool with session cache; drop heavy-serial parse gate in spool
  mode; parse concurrency matches thread count
- Streaming terrain: batched parallel parse+bake, scan/bake pipeline, shape
  spool with persistent buffered I/O and flush-before-read
- Parallel flat-file streaming for models/includes; pack/model spool for
  low-memory incremental flush
- Optional 50 GB private-bytes guard during headless bake

Braniewo_szeroki: 160 modules, verify PASS, ~34s bake (nmt100 ~17s vs ~190s
serial baseline).

Co-authored-by: Cursor <cursoragent@cursor.com>

scene/eu7/v2/eu7v2_load.h

@@ -0,0 +1,36 @@
+/*
+This Source Code Form is subject to the
+terms of the Mozilla Public License, v.
+2.0. If a copy of the MPL was not
+distributed with this file, You can
+obtain one at
+http://mozilla.org/MPL/2.0/.
+*/
+
+#pragma once
+
+#include <cstdint>
+#include <vector>
+
+namespace scene::eu7 {
+struct Eu7Scene;
+struct Eu7Module;
+} // namespace scene::eu7
+
+namespace eu7v2 {
+
+// Reconstructs a parsed scene from an eu7v2 container produced by bake_scene()
+// / bake_module(). The reconstructed Eu7Scene can be fed to the existing apply
+// path, so switching to the new format only swaps serialization and reuses the
+// proven world-construction code. Returns false on a malformed container (the
+// scene is left in a partially-populated but safe state).
+[[nodiscard]] bool
+load_scene( std::uint8_t const *data, std::size_t size, scene::eu7::Eu7Scene &out );
+
+// Reconstructs a full module (scene + includes + placement + flags) from an
+// eu7v2 container. The runtime needs the includes to recurse into child
+// modules. Returns false on a malformed container.
+[[nodiscard]] bool
+load_module( std::uint8_t const *data, std::size_t size, scene::eu7::Eu7Module &out );
+
+} // namespace eu7v2