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>

application/application.h

@@ -36,6 +36,12 @@ public:
         init( int Argc, char *Argv[] );
     int
         run();
+    // Headless text -> eu7v2 bake (+optional roundtrip verify). Runs without a
+    // window / renderer / audio. Returns a process exit code (0 == OK).
+    static bool
+        wants_eu7v2_headless( int Argc, char *Argv[] );
+    static int
+        run_eu7v2_headless( int Argc, char *Argv[] );
     // issues request for a worker thread to perform specified task. returns: true if task was scheduled
 
     #ifdef WITH_DISCORD_RPC