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_bake.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 {
+
+// Bakes a parsed scene (output of the text parser) into a self-contained
+// eu7v2 "sim" container: STRS + PROT/INST (deduplicated models) + MESH
+// (terrain) + SHPE/LINE + simulation record chunks. This is the clean-slate
+// replacement for the legacy EU7B emitter; it reuses the existing parser
+// front-end and only changes the on-disk representation.
+[[nodiscard]] std::vector<std::uint8_t>
+bake_scene( scene::eu7::Eu7Scene const &scene );
+
+// Lossless module bake: everything bake_scene() emits, plus INCL (includes
+// for recursion) and META (flags, placement, first_init_count). This is the
+// format the runtime loads as a module.
+[[nodiscard]] std::vector<std::uint8_t>
+bake_module( scene::eu7::Eu7Module const &module );
+
+} // namespace eu7v2