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.

docs/hd-art.md

@@ -2,7 +2,7 @@
 
 The Rust Options screen includes **HD art**. It starts disabled. Enable it to use reviewed artwork from the selected data directory's `hd/hd.json`; each missing or rejected frame keeps the selected original / 2x / 3x / 4x crisp treatment. The bundled runtime uses `data/`, while development artwork and review jobs live under `../data/`. The scale setting still determines the indexed rendering resolution, and the HD toggle can be changed while paused. HD art is presentation only: simulation, collision sizes, banking positions and save content IDs stay unchanged.
 
-Current coverage — 18 October 2026: the optional HD pack contains **5,521 reviewed pictures in 3,650 complete sequences**; **232 originals still await approval**. This append contains five Enemy, six Terrain and ten UI/other pictures: 19 derived cleanups plus two exact Source aliases. Controlled poses, genuine finite Terrain contexts, the legacy ORDER template and catalogue-only scopes remain distinct. Retained generated parents, literal functional Original samples and prior HOLDs remain separately recorded. The [HD backlog](hd-backlog.md) records exact scopes and remaining work; earlier observations below are historical.
+Current coverage — 18 October 2026: the optional HD pack contains **5,539 reviewed pictures in 3,668 complete sequences**; **214 originals still await approval**. This append contains 18 derived Terrain pictures: two selected small tiles and the complete organic forest16 family. Full-family intrinsic and finite genuine contexts retain their distinct sampled/independent roles, fixed-H5500 pixel epoch and actual-H5521 input carries. All previous generated parents and material HOLDs remain separately recorded. The [HD backlog](hd-backlog.md) records exact scopes and remaining work; earlier observations below are historical.
 
 Historical 17 October 2026 document-freeze observation: The external and assembled shared runtime pack contains **5,384 reviewed original picture frames / 3,551 complete sequences**, including **4,275 Terrain pictures**. **369 of 5,753 original pictures remain**: 260 Terrain, 75 enemies/ground objects, 33 UI/other and one boss. This six-frame append adds Boss 200ba, Terrain 2039a and the complete four-frame TANK03G3 family 3007c–3007f in three native sequences / three unchanged raw PNGs. Five hybrid frames explicitly retain 207 Original logical cells: 11 in 200ba and 50/48/49/49 across Tank phases; those cells are not generated HD. All previous 5,378 bindings and the full 3,548-header prefix remain exact, including canvas, origin, crop and optional-field presence. The assembled data contains **9,335 files / 8,179,315,857 bytes**. Actual CLI validates all 5,384 frames with zero rejects and 45 mods/one override (`2f3ab585`). Source18 and both binaries remain unchanged at API-B; future Source-C work is not the current runtime. Different reviews cover one genuine 200ba pose, all four naturally observed Tank phases and exactly two 2039a contexts; no all-placement or seamless-road claim follows. Visible 2039a edge and texture steps remain qualified, and the other 14 road tiles remain held. Previous 5,378 publication is remote-confirmed at `9ba0a5c7`. Native Windows 5,341 passed 360 tests with zero failures and 26 ignored; the separate campaign c4a4 run's old-test failure is preserved, while the 58723547 correction's native Windows workflow is still packaging. Publication and native Windows execution for 5,384 remain pending. Neither Windows result is relabeled as 5,378/5,384 execution; full HD completion remains open.