feat(simulation): quarter street network — typed corridors/access/lattice (#957)

Complete the Layer-4 quarter geometry with the street layer (D-234), replacing
the ChunkLayout/CorridorSpine/AccessPoint String stubs with real types:
- AccessPoint{position,kind} + AccessKind (QuarterEdge/ReservationGate/
  BlockJunction): the quarter's road nodes (from road_entry_directions octants +
  reservation gates), the node set the D-097 audit reads.
- CorridorSpine{from,to,path}: arterial trunk edges, ±45°-snapped polylines
  (D-096 cap). Topology gated by morphology (D-234a): Ribbon (fjord/canyon/
  mountain-pass), HubSpoke (delta/island/enclosed water), Mesh/Prim-MST
  (plains/meander/coastal). A spanning tree over the access nodes.
- ChunkLayout{spacing,offset,rotation_steps}: per-block local ±45° lattice,
  spacing from density, offset/rotation modulated by the D-096 Grid/Organic mode.

Wired into generate_quarter_skeleton (access_points + corridors + per-block
chunk_layout). All integer-deterministic (D-010). 7 new tests.

Remaining D-234 piece: the per-edge waterfront pier/quay rule needs Layer-1
terrain water-adjacency threaded to the skeleton (cross-layer plumbing).

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

server/src/simulation/generator.rs

@@ -50,10 +50,8 @@ pub type Era = String;
 pub type EraModification = String;
 /// Landmark slot description within a block. Stub.
 pub type LandmarkSlot = String;
-/// Chunk layout specification within a block (how the 2×2 chunks are arranged). Stub.
-pub type ChunkLayout = String;
-/// Corridor spine connecting district access points. Stub.
-pub type CorridorSpine = String;
+// `ChunkLayout`, `CorridorSpine`, `AccessPoint` are typed street-network structs
+// (D-234, #957) — see the "Street-network types" section below.
 /// District context — neighboring districts, world position, system. Stub.
 pub type QuarterContext = String;
 /// Society profile reference (Miri's cultural ingredients). Stub.
@@ -64,8 +62,56 @@ pub type ZoneDefinition = String;
 pub type QuarterBoundaries = String;
 /// Guarantee audit result — tier-appropriate spatial invariant checks. Stub.
 pub type GuaranteeAuditResult = String;
-/// District access point (entry/exit to neighboring district). Stub.
-pub type AccessPoint = String;
+// ---------------------------------------------------------------------------
+// Street-network types (D-234, #957)
+// ---------------------------------------------------------------------------
+
+/// Where a quarter's street network connects to the outside, to a reservation,
+/// or to an interior junction (D-234). These are the nodes the arterial graph
+/// spans and the guarantee audit (D-097) reads.
+#[derive(Serialize, Deserialize, Clone, Debug, PartialEq, Eq)]
+pub struct AccessPoint {
+    /// Tile-space position within the 512-tile quarter (0–511).
+    pub position: (u16, u16),
+    pub kind: AccessKind,
+}
+
+/// Kind of [`AccessPoint`] (D-234).
+#[derive(Serialize, Deserialize, Clone, Debug, PartialEq, Eq)]
+pub enum AccessKind {
+    /// Road enters the quarter from outside at a compass octant (0=N…7=NW),
+    /// from `CityGenerationContext.road_entry_directions`.
+    QuarterEdge { octant: u8 },
+    /// Gate into a multi-block reservation.
+    ReservationGate { reservation: ReservationId },
+    /// Internal junction between blocks.
+    BlockJunction,
+}
+
+/// One arterial spine — a ±45°-snapped edge of the quarter's trunk-road graph
+/// (D-234 refined: arterials = least-cost graph over the access nodes). `from`/`to`
+/// index into the quarter's `access_points`; `path` is the tile-space polyline
+/// (segments axis- or 45°-aligned, D-096 ±45° cap). This node/edge graph is what
+/// the guarantee audit (D-097) reads as the trunk topology.
+#[derive(Serialize, Deserialize, Clone, Debug, PartialEq, Eq)]
+pub struct CorridorSpine {
+    pub from: u16,
+    pub to: u16,
+    pub path: Vec<(u16, u16)>,
+}
+
+/// Local street lattice descriptor for one block (D-234 refined: local streets =
+/// a ±45° grid lattice within each block, modulated by the D-096 layout mode).
+/// A compact parametric form the fill layer rasterizes — not the raster itself.
+#[derive(Serialize, Deserialize, Clone, Debug, PartialEq, Eq, Default)]
+pub struct ChunkLayout {
+    /// Street spacing in tiles (the block is divided into spacing-sized cells).
+    pub spacing: u8,
+    /// Lattice origin offset in tiles (organic jitter; `(0,0)` for grid).
+    pub offset: (u8, u8),
+    /// Rotation in 15° steps (0–3 ⇒ 0–45°, the D-096 cap; 0 for grid).
+    pub rotation_steps: u8,
+}
 /// Base visual palette for a zone. Stub.
 pub type BasePalette = String;
 /// Economic modifier on a zone palette. Stub.