feat(simulation): BuildingExteriorTag grammar + Layer-5 material fill + ops-surface (T-988/T-959/T-1097)

T-988 — BuildingExteriorTag {wall_material, roof_form, facade_rhythm,
setback_tier, color:HsvColor, street_surface}. New trait_exterior.rs:
3-step era-free derivation (visual_bundle filter -> zone-bias weighted
pick -> density->setback), color seed-sampled within the register band.
Resolved at GenerateSkeleton plan time (T-994 precedent), frozen on
BuildingPropertyTag; FillChunk only reads it. Four append-only
integer-discriminant enums (WallMaterial/RoofForm/FacadeRhythm/
StreetSurface), unknown token -> axis Generic + warn. trait_catalog_reader
now parses visual_bundle + the two new tables (OnceLock-cached).
New SeedDomain::TraitExterior (per-axis sub-chains — no cross-field
correlation).

T-959 — FillChunk reads the frozen exterior tag: wall_material/roof_form
onto Wall/Roof shell voxels (FilledChunk.surface_material). Additive,
ShellVoxel untouched, all shell tests pass. (Interstitial-fill-from-setback
split to T-1098 — needs a FillChunk block-metadata + geometry design pass;
nothing consumes FillChunk until Phase 5.)

T-1097 — BlockSkeleton.interstitial_character (OpenSpace|OperationsSurface),
D-233 bulk-driven: bulk-industry blocks' non-roofed remainder tags as built
economic infrastructure, not generic open space.

cargo check --all-targets clean; 1666 lib tests pass; no golden impact
(harnesses top out at CascadeLayer::RoadGraph, unreachable by Layer 4/5).

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

server/src/atlas/gen_queue.rs

@@ -34,6 +34,7 @@ use crate::atlas::district_profile::BodyParams;
 use crate::atlas::heightmap::{load_heightmap_png, GRID_H, GRID_W};
 use crate::atlas::shell::{fill_chunk, FilledChunk};
 use crate::atlas::skeleton_gen::{assign_all_block_tags, generate_quarter_skeleton};
+use crate::atlas::trait_catalog_reader::ExteriorCatalog;
 use crate::seed::SeedChain;
 use crate::simulation::generator::{BuildingPropertyTag, CityGenerationContext, QuarterWorldState};
 
@@ -113,6 +114,15 @@ pub enum GenWorkItem {
         economic_role: String,
         population: i64,
         founding_age_years: u32,
+        /// D-235 exterior-grammar content (T-988): the trait-template catalog's
+        /// `visual_bundle`s plus the two sibling content tables
+        /// (`architecture_zone_bias`, `color_register_bands`), pre-resolved at
+        /// dispatch time — mirrors `context`'s own pre-resolution rationale, so
+        /// `assign_block_tags` never touches `systems.db` (T-987/D-230 purity).
+        /// A `Vec`/`BTreeMap`-backed struct is a handful of words on the stack
+        /// regardless of its contents' size (same reasoning already documented
+        /// for `FillChunk.block_tags` below), so this needs no `Box`.
+        exterior_catalog: ExteriorCatalog,
     },
     /// Derive the building shell for one 64 m chunk of an existing quarter
     /// (D-230 derive phase, T-987).
@@ -431,6 +441,7 @@ fn run_work_item(item: &GenWorkItem) -> GenCompletion {
             economic_role,
             population,
             founding_age_years,
+            exterior_catalog,
         } => {
             // Build the Phase 1 skeleton from the pre-resolved D-199 context.
             // `economic_role`, `population`, and `founding_age_years` are the
@@ -445,13 +456,16 @@ fn run_work_item(item: &GenWorkItem) -> GenCompletion {
                 *chain,
             );
             // Step-3 building-property tags per footprint (D-229, #957): subdivide
-            // each block into building plots and tag them.
+            // each block into building plots and tag them. `exterior_catalog`
+            // (D-235, T-988) resolves each tag's BuildingExteriorTag in the
+            // same pass.
             let block_tags = assign_all_block_tags(
                 &skeleton,
                 context,
                 economic_role,
                 *founding_age_years,
                 *chain,
+                exterior_catalog,
             );
             GenCompletion::SkeletonGenerated {
                 city_id: *city_id,
@@ -591,6 +605,7 @@ mod tests {
             economic_role: "service_mixed".to_string(),
             population: 500_000,
             founding_age_years: 200,
+            exterior_catalog: ExteriorCatalog::default(),
         }
     }
 
@@ -700,8 +715,10 @@ mod tests {
     fn quarter_with_one_building() -> QuarterWorldState {
         use crate::atlas::tile_condition::TileCondition;
         use crate::simulation::generator::{
-            ArchitectureFlavorRef, BuildingEntryClass, BuildingPropertyTag, ConstructionEra,
-            EraCause, FloorExtent, FloorHeightProfile, QuarterSkeleton, TileRect, ZoneTypeId,
+            ArchitectureFlavorRef, BuildingEntryClass, BuildingExteriorTag, BuildingPropertyTag,
+            ConstructionEra, EraCause, FacadeRhythm, FloorExtent, FloorHeightProfile, HsvColor,
+            QuarterSkeleton, RoofForm, SetbackTier, StreetSurface, TileRect, WallMaterial,
+            ZoneTypeId,
         };
         use std::collections::BTreeMap;
 
@@ -721,6 +738,18 @@ mod tests {
                 era: ConstructionEra::Founding,
                 era_cause: EraCause::Original,
                 initial_condition: TileCondition::Intact,
+                exterior: BuildingExteriorTag {
+                    wall_material: WallMaterial::Generic,
+                    roof_form: RoofForm::Generic,
+                    facade_rhythm: FacadeRhythm::Generic,
+                    setback_tier: SetbackTier::Standard,
+                    color: HsvColor {
+                        hue: 0,
+                        sat: 0,
+                        val: 5_000,
+                    },
+                    street_surface: StreetSurface::Generic,
+                },
                 doors: Vec::new(),
             }],
         );