Find a ten-entry table on a 148-byte stride after shrub

Range measured: level 0, 16047040..16737344, the 690,304 bytes between the
last shrub class's body and the constant trailer. Nothing outside that range
is read.

Method: reading the bytes at +0x20 as u32 shows ten consecutive entries
whose low halves increase by a constant 0x94 (148), followed by a zero. The
high half is 0xf000 for the first nine and 0x0a40 for the tenth, so the
table is ten entries and ends at +0x48, absolute 16047112.

What the entries mean, what 148 refers to, and why there are ten are all
unestablished. Ten matches no count already known for this level -- 238
moby classes, 74 tie, 7 shrub, 93 tfrag textures -- so it is not yet tied
to anything else in the lump.

Recording it as a lead rather than a finding. The stride is a real
measurement on a bounded range, but a ten-entry table with an unexplained
stride is exactly the shape that looks like a structure while being
something else, and the rule in AGENTS.md is that a pattern gets looked at
before it gets named.

docs/formats/core-data-regions.md

@@ -150,3 +150,21 @@ range and was about to conclude the body had zero length, which would have been
 wrong. The last shrub class is a real class with real data, and the NaN filler
 only appears in degenerate ones. Checking the actual byte pattern rather than
 concluding from a failed heuristic is what caught it.
+
+### First structure in the region after shrub
+
+**Range measured:** level 0, `16047040 .. 16737344` (690,304 bytes), starting
+at the first byte after the last shrub class's 240-byte body. Nothing outside
+that range is read.
+
+**Method:** reading the bytes at `+0x20` as `u32` shows ten consecutive
+entries whose low halves increase by a constant **0x94 (148)**, followed by a
+zero. Read as u32 the high half is `0xf000` for the first nine and `0x0a40`
+for the tenth, so the table is ten entries long and ends at `+0x48`
+(absolute `16047112`).
+
+**Result, stated plainly:** a ten-entry table on a 148-byte stride. What the
+entries mean, what 148 refers to, and why there are ten, are all unestablished.
+Ten does not match any count already known for this level -- 238 moby
+classes, 74 tie, 7 shrub, 93 tfrag textures -- so this is not yet tied to any
+structure elsewhere in the lump.