docs+tool(assembler): round L17 report; readable shading in the Linux capture tool

The capture tool gains --shade=readable (directional light, soft ambient, height tint) and an
optional --tile-edges overlay; display only. The L17 Core fix is NOT merged: its owner/Core chunk
scale change (8 m -> 4 m) moves every stratum and leaves the SurfaceWorld spawn camera over a void
(reviewer before/after renders). Kept on wip/l17-fi-scale. The FloatingIslands full-XY
boundarySeal cap is the likely real cause of the false floors and needs a separate minimal fix.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01CSFYgsdW8ejZSyiMf4qRSX

Standalone/Research/WorldAssemblerM3/Linux17/OWNER_NOTE.md

@@ -0,0 +1,26 @@
+# Owner note — L17 FloatingIslands steps
+
+The ledges were real generated mesh geometry caused by two boundary mistakes that made empty space
+look like flat ground: the FloatingIslands seal was applied as a solid cap across XY, and owner
+chunks were treated as 8 m of Core voxels instead of their actual 4 m. At the measured flat square,
+the native island field is air and cave/floor influence is zero. The point is about 100 m from the
+four islands.
+
+I removed the false cap and corrected the shared owner/Core coordinate conversion. Evaluator version
+is 7. The before/after captures show the false sheet disappear and the actual island shape remain.
+SurfaceWorld’s L1 hash changes because it now selects its intended `Heightfield2D` route; its route,
+readiness and proof audits pass.
+
+The export has nonempty meshes at LOD0–8, and the standalone viewer enables and draws all levels by
+default. I cannot identify the screenshot’s dark square as a whole missing LOD from the Linux data;
+it may be a specific tile or viewer draw/upload issue. I did not change the Windows viewer. Please
+capture the view below and, if the square remains, repeat with `--capture-only-lod=0` through `8`.
+
+The low-view camera is `(-22,-19,-22.8) m`, yaw 0°, pitch −4°, matching the Linux island pair.
+
+```bat
+VoxelForgeCoreStandalone.exe --world-assembler-prototype --recipe=floating-islands --clip-radius=3 --max-clip-level=8 --workers=12 --camera=-22,-19,-22.8,0,-4 --capture=Standalone\Research\WorldAssemblerM3\Linux17\captures\floating-islands-windows.png --frame-limit=60
+```
+
+Use a different `--capture=` filename for each isolated LOD. Send the all-level image plus the
+isolated image that corresponds to the square.