re: withdraw "the speed cannot be used", and close the world-unit item

Last iteration I ruled the speed route out because the emulator is not real-time
so the wall-clock denominator is unknown.  Wrong: the game prints its own clock,
and flight-speed-law.md had already used it -- mission TIME across a wall interval
gives 1.26x, turning 443.6 units/wall-second into 352 per game-second against a
HUD 350.  Withdrawn in place, with the reasoning, rather than deleted.

Closes the backlog item: one world unit is one metre, by two independent routes.

docs/re/BACKLOG.md

@@ -86,6 +86,15 @@ See [`mission-freeze-heap-exhaustion.md`](mission-freeze-heap-exhaustion.md).
   between tool calls.** Sequential tool calls *within* one turn are fine; it is
   ending the turn that kills it.
 
+✅ **The world-unit measurement is DONE — one world unit is one metre.** Two
+independent routes: the `mapmesh_box_500km` collision hull is a cube of exactly
+500 000.0 units per axis (and the other box mesh exactly 100 000.0), and
+[`flight-speed-law.md`](flight-speed-law.md) gives 352 units per game-second
+against a HUD reading of 350. The `CollisionSet` objection that forced the 🟡 is
+dismantled in [`structures/mcol-collision.md`](structures/mcol-collision.md): it
+read the four-member `rob_` family (which contains a 50 km "player fighter") as
+if it were hull sizes, and 133 m is the 7th smallest of 78 `rou_` meshes.
+
 ❔ **The world-unit measurement is still not made** — but the blocker under it is
 now GONE. The entity scan works: see
 [`entities-live-roster.md`](entities-live-roster.md), **13 unit definitions and 42

docs/re/world-unit-attempt-2026-08-26.md

@@ -63,13 +63,35 @@ destroyer produced no candidate at all, so the offset is not yet shown to be
 uniform across instances — and `+0x29d4` in the same object is the same bytes
 read one float over, which is an artifact, not a second hit.
 
-❌ **The speed cannot be used as the corroborating measurement**, tempting as it
-is. 116.6 units per 0.6 s *wall-clock* against the HUD's `350` would give a unit
-directly — but the emulator does not run at real time under lavapipe, so the
-denominator is unknown. Recording this so the next attempt does not spend an
-iteration on it.
+> ### ❌ WITHDRAWN — "the speed cannot be used" was wrong
+>
+> This section originally said the speed route was unusable because the emulator
+> does not run at real time under lavapipe, so the wall-clock denominator is
+> unknown. **The denominator is not unknown: the game prints its own clock.**
+> [`flight-speed-law.md`](flight-speed-law.md) had already done exactly this
+> measurement, and more carefully — mission `TIME` read off the HUD across a
+> wall-clock interval gives the ratio (**1.26×**), and 443.6 units per
+> wall-second becomes **352 per game-second** against a HUD reading of **350**.
+>
+> I wrote the route off instead of checking whether the corpus had already
+> walked it. That is the *same* mistake logged twice above on this page, so it
+> is recorded here rather than quietly deleted.
 
-## ❔ Still not measured: the unit
+## ✅ SETTLED — the unit is the metre
+
+Measured this run, statically: the `mapmesh_box_500km` hull is a cube of
+**exactly 500 000.0 units** on every axis (`−250 000 … +250 000`), and the only
+other box-shaped MCOL is exactly **100 000.0** — the same ruler at a different
+size. Together with the dynamic confirmation above (352 units per game-second
+against a HUD 350) and the dismantling of the `rob_`/`rou_` size objection in
+[`structures/mcol-collision.md`](structures/mcol-collision.md):
+
+> **one world unit is one metre.**
+
+The paragraph below is kept as written, because it is what was still open at the
+time and it records the plan that turned out to be unnecessary.
+
+## ❔ (superseded) Still not measured: the unit
 
 The measurement needs a **locked target**, so the HUD prints a numeric range to a
 specific entity whose position can be read at the same moment. This run never