Remaster eighteen original terrain pictures

Add the complete organic forest family and two Source-guided terrain tiles with portable reproduction tools and review evidence. Preserve existing game assets and restore fifteen referenced archival metadata files.

Validation: 157 maintained HD-tool tests; installed HD validation 5539/5539 with zero rejects; 45 mods; three 1080p SDL controls unchanged. SourceF binaries and gameplay are unchanged. Native Windows validation for the preceding 5521-picture commit passed.

runtime-windows-manifest.json

@@ -3,7 +3,7 @@
   "platform": "Windows x86_64",
   "target": "x86_64-pc-windows-gnu",
   "catalog_entries": 6449,
-  "approved_hd_frames": 5521,
+  "approved_hd_frames": 5539,
   "shared_data_manifest": "runtime-manifest.json",
   "dependencies": {
     "raptor-rust.exe": [