feat(simulation): T-1127 glaciation ice tint + Marine color in zoom-ladder probe

aliveness_probe --render gains a 6th glaciation panel; glaciated
districts get an ice tint keyed on GlaciationGrade, and Marine
vegetation renders [0,96,172] — distinct from the morphology water
tones so district-carrier vs voxel-generator disagreement stays
visible in ladders.

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

server/src/bin/aliveness_probe.rs

@@ -37,7 +37,8 @@ use settled_reach_server::atlas::believability::{
 use settled_reach_server::atlas::body_world_state::BodyWorldState;
 use settled_reach_server::atlas::chunk_context::derive_chunk_context;
 use settled_reach_server::atlas::district_profile::{
-    derive_district, BodyParams, ClimateConstants, DistrictProfile, VegetationClass,
+    derive_district, BodyParams, ClimateConstants, DistrictProfile, GlaciationGrade,
+    VegetationClass,
 };
 use settled_reach_server::atlas::features::TerrainAnalysis;
 use settled_reach_server::atlas::scale::{
@@ -335,8 +336,17 @@ const MORPHOLOGY_RGB: [[u8; 3]; 17] = [
     [64, 115, 102],  // 16 Wetland
 ];
 
-/// The five attribute panels, in output order.
-const PANEL_NAMES: [&str; 5] = ["morphology", "elev", "temp", "moisture", "veg"];
+/// The attribute panels, in output order. `glaciation` is T-1127's dedicated
+/// panel; the morphology panel additionally carries a per-pixel ice tint keyed
+/// on the same field (see [`apply_ice_tint`]).
+const PANEL_NAMES: [&str; 6] = [
+    "morphology",
+    "elev",
+    "temp",
+    "moisture",
+    "veg",
+    "glaciation",
+];
 
 /// Render the district window around the principal settlement and write one PNG
 /// per panel to `out_dir`, plus a one-line manifest per image and a determinism
@@ -447,7 +457,7 @@ fn render_window_panels(
 ) -> Vec<(&'static str, Vec<u8>)> {
     let n_i = n as i32;
     let half = n_i / 2;
-    let mut bufs: [Vec<u8>; 5] = std::array::from_fn(|_| vec![0u8; (n * n) as usize * 3]);
+    let mut bufs: [Vec<u8>; 6] = std::array::from_fn(|_| vec![0u8; (n * n) as usize * 3]);
     for row in 0..n_i {
         for col in 0..n_i {
             // Row 0 = northmost: smaller dy = further north (derive_district maps
@@ -455,11 +465,19 @@ fn render_window_panels(
             let dp = (centre.0 - half + col, centre.1 - half + row);
             let prof = derive_district(seed, body_id, params, ta, dp, climate);
             let i = ((row * n_i + col) * 3) as usize;
-            set_rgb(&mut bufs[0], i, morphology_rgb(prof.morphology_zone));
+            // T-1127: the morphology color carries a per-pixel ice tint keyed on
+            // glaciation_grade (a render modifier — the frozen D-239 §6 zone
+            // vocabulary is untouched; tint = classifier-tuning territory).
+            set_rgb(
+                &mut bufs[0],
+                i,
+                apply_ice_tint(morphology_rgb(prof.morphology_zone), prof.glaciation_grade),
+            );
             set_rgb(&mut bufs[1], i, gray_rgb(prof.elev_q));
             set_rgb(&mut bufs[2], i, temperature_rgb(prof.temperature_c));
             set_rgb(&mut bufs[3], i, moisture_rgb(prof.moisture_q));
             set_rgb(&mut bufs[4], i, vegetation_rgb(prof.vegetation_class));
+            set_rgb(&mut bufs[5], i, glaciation_rgb(prof.glaciation_grade));
         }
     }
     for buf in &mut bufs {
@@ -566,6 +584,43 @@ fn vegetation_rgb(v: VegetationClass) -> [u8; 3] {
         VegetationClass::Forest => [30, 110, 40], // closed canopy
         VegetationClass::RiparianScrub => [70, 170, 120], // waterway band (open)
         VegetationClass::RiparianThicket => [10, 130, 90], // waterway band (dense)
+        // T-1126: open water — an ocean blue deliberately DISTINCT from the
+        // morphology water tones (OpenOcean 26,51,115 / Lake 51,102,166) so a
+        // veg-panel Marine cell is never mistaken for a morphology overlay.
+        VegetationClass::Marine => [0, 96, 172],
+    }
+}
+
+/// T-1127: blend the morphology color toward glacial ice-white by
+/// `glaciation_grade` — a RENDER modifier only (the D-239 §6 frozen 17-zone
+/// vocabulary is untouched; an actual ice zone would need its own D-amendment).
+///
+/// `Light` deliberately does NOT tint: grade 1 is glacial-erosion *signatures*
+/// (U-valleys, moraines — landform history on coasts as warm as +5 °C mean),
+/// not ice cover; visible ice starts where D-239 §5 gates glacial forms,
+/// grade ≥ Moderate. The dedicated glaciation panel still shows Light.
+fn apply_ice_tint(base: [u8; 3], grade: GlaciationGrade) -> [u8; 3] {
+    let t = match grade {
+        GlaciationGrade::None | GlaciationGrade::Light => return base,
+        GlaciationGrade::Moderate => 0.30,
+        GlaciationGrade::Heavy => 0.50,
+        GlaciationGrade::IceCap => 0.70,
+    };
+    lerp_rgb(
+        [base[0] as f32, base[1] as f32, base[2] as f32],
+        [228.0, 240.0, 250.0], // glacial ice white-blue
+        t,
+    )
+}
+
+/// T-1127: dedicated glaciation panel — categorical dark→ice ramp.
+fn glaciation_rgb(grade: GlaciationGrade) -> [u8; 3] {
+    match grade {
+        GlaciationGrade::None => [30, 30, 30],
+        GlaciationGrade::Light => [96, 120, 150],
+        GlaciationGrade::Moderate => [150, 180, 210],
+        GlaciationGrade::Heavy => [200, 222, 240],
+        GlaciationGrade::IceCap => [240, 248, 255],
     }
 }