re: RESTORE "one world unit is one metre" -- the objection conflated two families

The 2026-08-26 downgrade rested on two numbers, and grouping the CollisionSet
names by prefix dissolves both:

 - The 447 km "largest object" is rob_f002_cmesh, one of only FOUR rob_ meshes
   (44k-448k).  That family is not hull size: rob_f001_bdy_cmesh measures 50179
   and f001 is the player's own Delta Saber, whose disc record gives Size_Radius
   10.0.  A 50 km player fighter is impossible under every unit convention, so
   rob_ spans something else entirely and is not evidence about the world unit.
 - The "small" 133 m craft is small: rou_e010_cmesh = 133.2 is the 7th smallest
   of 78 rou_ meshes (median 636.2, max 9534.9).  Against its own family, the
   game calling e010 small AGREES with the metre.

Measured this run: the 500 km box is a cube of exactly 500000.0 units on every
axis (+-250000), and the second box mesh is exactly 100000.0 -- the same ruler.

Independent dynamic confirmation already in the corpus (flight-speed-law.md):
443.6 world units per wall-second, mission clock 1.26x wall, so 352 units per
game-second against a HUD reading of 350.

docs/re/structures/mcol-collision.md

@@ -544,12 +544,46 @@ The arithmetic is exact and it runs the other way as a check on the format work:
 a wrong stride or index width could not have produced a box whose measured size
 matches its own filename.
 
-> 🟡 **Downgraded 2026-08-26, same day.** The *format* check stands. The
+> 🟡 **Downgraded 2026-08-26.** The *format* check stands. The *interpretation*
-> *interpretation* does not: decoding `CollisionSet_*.bin` gave the first chance
+> does not: decoding `CollisionSet_*.bin` gave the first chance to see what a
-> to see what a metre implies, and it makes a craft the game's own tables call
+> metre implies, and it makes a craft the game's own tables call "small" 133 m
-> "small" 133 m long and the largest object 447 km — 89 % of the arena. Either
+> long and the largest object 447 km — 89 % of the arena. Either the ships really
-> the ships really are kilometre-scale or `500km` names something other than the
+> are kilometre-scale or `500km` names something other than the span. See
-> span. See [`collisionset.md`](collisionset.md).
+> [`collisionset.md`](collisionset.md).
+>
+> ## ✅ **RESTORED the same day — the objection was reading two different families as one**
+>
+> Both halves of the objection dissolve once the `CollisionSet` names are grouped
+> by prefix (`tools/re-capture/collisionset.py list`, bbox diagonals):
+>
+> | prefix | n | min | median | max |
+> |---|---|---|---|---|
+> | `rou_` | 78 | 51.8 | 636.2 | 9 534.9 |
+> | `mob_` | 30 | 363.2 | 1 523.0 | 17 288.3 |
+> | `S0*` (asteroid fields) | 29 | 18 885.4 | 39 752.2 | 84 713.5 |
+> | **`rob_`** | **4** | **44 378.7** | **50 179.3** | **447 521.9** |
+>
+> * **The 447 km "largest object" is `rob_f002_cmesh`, from the four-member
+>   `rob_` family — and that family is not ship dimensions at all.** The proof is
+>   inside it: `rob_f001_bdy_cmesh` measures **50 179**, and `f001` is the
+>   *player's own Delta Saber*, whose disc record gives `Size_Radius` **10.0**. A
+>   50 km player fighter is impossible under *every* unit convention, metres
+>   included, so whatever `rob_` spans — spawn volumes, route bounds — it is not
+>   hull size. It cannot be evidence about the world unit either way.
+> * **The "small" 133 m craft is small.** `rou_e010_cmesh` = 133.2 is the
+>   **7th smallest of the 78** `rou_` meshes, against a family median of 636.2 and
+>   a max of 9 534.9. Read against its own family rather than against intuition,
+>   the game calling `e010` small agrees with the metre exactly.
+>
+> And the metre now has a second, fully independent confirmation from the dynamic
+> side — see [`../flight-speed-law.md`](../flight-speed-law.md): 20 s of straight
+> neutral-throttle flight covers **443.6 world units per wall-second**, the mission
+> clock runs **1.26×** wall time, and 443.6 / 1.26 = **352 units per game-second**
+> against a HUD reading of **350**. A static box named 500 km measuring 500 000.0
+> units, and a HUD speed matching displacement per game-second, are two unrelated
+> routes to the same answer.
+>
+> > **✅ CONFIRMED: one world unit is one metre.**
 
 Reproduce with `tools/re-capture/miscbin_names.py <extract root> [--pairs]`
 (recorded in [`../data/miscbin-names.txt`](../data/miscbin-names.txt)).