fix(simulation): PR #194 review round — rung-floor dependency direction, golden body coverage, doc honesty

Tyre's I1 (his ruling: the cutoff's job is Nyquist, a property of the
RUNG): MIN_WL_BANDS_M's District band now derives from 2*DISTRICT_M
directly, decoupled from OCTAVE_WAVELENGTHS_M[3] — a detail_scatter
retune can no longer silently redefine the Atlas rung floor. Direction-
agnostic const assert pins the coincidence so drift on either side
breaks the build for a deliberate human decision; golden_cutoffs_match_
the_scale_ladder now pins the District coupling too. I2: D-226
paraphrase replaced with cites to the T-1150 wire-contract note +
T-1162 refinement resolution (2), plus a self-found stale 2048m claim
fixed in the same comments. I4: golden extended with airless/dry
(ceiling_q==0 short-circuit) and volcanic-coast (ridged warp) body
rows via body_sweep_samples() — fixture regen verified 510 insertions,
0 deletions (existing rows byte-identical, purely appended). Q2 nit:
vegetation_invention module doc now states majority-preservation as
the coherence guarantee, not per-cell class stability (a boundary
cell's flip IS the clearing mechanism). Forward-contract for T-1156:
0x5EED_C0DE promoted to named WINDOW_RELIEF_SALT const. 158 focused
tests green; cargo check --tests clean.

Tickets: T-1162, T-1161

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

server/src/atlas/layer_proxy.rs

@@ -405,17 +405,27 @@ fn clamp_window_n_v2(raw_n: u32, granularity: WindowGranularity) -> u32 {
 }
 
 /// Quantized `window_min_wl_m` bands (T-1150, zoom ladder design doc §5;
-/// retuned T-1162 part (c)): `0` (no cutoff) plus every entry of
-/// [`crate::atlas::detail_scatter::OCTAVE_WAVELENGTHS_M`] (32,768/16,384/
-/// 8,192/4,096 m — District's own Nyquist floor, `2 × DISTRICT_M`), plus a
-/// FIFTH band at `1,024` m — Quarter's own Nyquist floor (`2 × QUARTER_M =
-/// 1,024`, matching a rung's content wavelength to what its `512` m sample
-/// spacing can actually resolve — nothing finer than the rung can express,
-/// nothing coarser than it deserves). `1,024` m is also the finest entry of
-/// the extended [`crate::atlas::coast_invention::WARP_OCTAVE_WAVELENGTHS_M`]
-/// band (T-1162 part a) and the coarsest entry of
-/// [`crate::atlas::detail_scatter::VOXEL_OCTAVE_WAVELENGTHS_M`] the sub-district
-/// relief wiring (T-1162 part b) admits at Quarter — one band serves both.
+/// retuned T-1162 part (c); band 4 re-derived per Tyre's PR #194 review I1).
+/// `0` (no cutoff) plus the two coarse legacy bands
+/// [`crate::atlas::detail_scatter::OCTAVE_WAVELENGTHS_M`]`[0..2]` (32,768/
+/// 16,384/8,192 m — carried over unchanged, no rung claims these as its own
+/// Nyquist floor), plus **District's own Nyquist floor** computed directly
+/// from the rung's spacing (`2 × DISTRICT_M = 4,096` m), plus **Quarter's own
+/// Nyquist floor** (`2 × QUARTER_M = 1,024` m).
+///
+/// **Dependency direction (Tyre, PR #194 I1):** the cutoff's semantic job is
+/// Nyquist truncation — a property of the RUNG (its sample spacing), never of
+/// any one invention field's octave choices. Band 4 is therefore derived from
+/// `scale::DISTRICT_M` directly, NOT from
+/// `detail_scatter::OCTAVE_WAVELENGTHS_M[3]` (the old T-1162 wiring) — that
+/// coupling ran backwards: a future `detail_scatter` retune could silently
+/// redefine the Atlas rung floor, and the coast warp already extends its OWN
+/// octaves below `OCTAVE_WAVELENGTHS_M`'s range (T-1162 part a), proving no
+/// single invention field's array is entitled to dictate the floor. The two
+/// values happen to coincide today (4,096 = `2 × DISTRICT_M` = also
+/// `OCTAVE_WAVELENGTHS_M[3]`) — the `const _: () = assert!(...)` immediately
+/// below pins that coincidence so a future drift on EITHER side breaks the
+/// build loudly instead of silently decoupling the two meanings.
 ///
 /// **Pre-T-1162 bands unchanged in VALUE** (32,768/16,384/8,192/4,096 stay
 /// exactly where they were) — but **NOT unchanged in behavior at 8,192/4,096
@@ -442,10 +452,25 @@ const MIN_WL_BANDS_M: [f64; 6] = [
     crate::atlas::detail_scatter::OCTAVE_WAVELENGTHS_M[0],
     crate::atlas::detail_scatter::OCTAVE_WAVELENGTHS_M[1],
     crate::atlas::detail_scatter::OCTAVE_WAVELENGTHS_M[2],
-    crate::atlas::detail_scatter::OCTAVE_WAVELENGTHS_M[3],
-    1_024.0,
+    2.0 * DISTRICT_M as f64,
+    2.0 * crate::atlas::scale::QUARTER_M as f64,
 ];
 
+/// Direction-agnostic guard (Tyre, PR #194 I1): `MIN_WL_BANDS_M`'s District
+/// band is now derived from `2 × DISTRICT_M`, deliberately decoupled from
+/// `detail_scatter::OCTAVE_WAVELENGTHS_M[3]` (see the doc above). The two
+/// values are expected to keep coinciding — `terrain_detail`'s finest octave
+/// IS meant to sit at District's Nyquist floor — but nothing in the type
+/// system enforces that anymore now that the dependency runs one direction
+/// only. This assert exists so that if either side ever drifts (a
+/// `detail_scatter` octave retune, or a `DISTRICT_M` scale-ladder change).
+/// the build breaks loudly and a human decides deliberately whether the
+/// coincidence should be restored or the two meanings were meant to diverge
+/// — never a silent redefinition of the Atlas rung floor.
+const _: () = assert!(
+    crate::atlas::detail_scatter::OCTAVE_WAVELENGTHS_M[3] as i64 == 2 * DISTRICT_M as i64
+);
+
 /// Snap a wire-supplied `window_min_wl_m` to the nearest fixed band in
 /// [`MIN_WL_BANDS_M`] (T-1150, design doc §5's gap-fix): "as specified,
 /// `window_min_wl_m` is viewport-continuous while the cache key/echo tuple is