feat(core): add ellipse ring and path repeat

docs/COMPONENT_DESIGN_GUIDE.md

@@ -69,6 +69,8 @@ Examples:
 - `SteppedTier`
 - `VerticalSetbackVolume`
 - `SteppedDome`
+- `EllipseRing`
+- `PathRepeat`
 - `ArcadeRun`
 - `TreeCanopy`
 - `OrganicPatch`
@@ -79,6 +81,8 @@ Examples:
 
 Add a high-level component only when it captures a reusable pattern that agents otherwise express verbosely or incorrectly.
 
+`EllipseRing` captures true bounded oval shells that cannot be represented by stadium caps without changing curvature. `PathRepeat` is deliberately limited to count-based ellipse sampling of a reusable assembly, reusing the existing arbitrary-angle instance rotation machinery. Keep the assembly Y local and apply global level offsets with non-negative integer `placement.y`; closed-loop `startAngle === endAngle` chooses a sampling phase without duplicating the seam. Keep the component semantics Minecraft-oriented; do not expand them into a general curve or CAD language.
+
 ## Component admission checklist
 
 Before adding a new component, answer all questions below.

docs/COMPONENT_PLAN_SPEC.md

@@ -197,6 +197,8 @@ Start with a small component vocabulary:
 - `VerticalSetbackVolume`
 - `SteppedDome`
 - `RectRing`
+- `EllipseRing`
+- `PathRepeat`
 - `RailingRun`
 - `ArcadeRun`
 - `SupportBracket`
@@ -243,6 +245,29 @@ Use `SteppedDome` for bounded Minecraft-style dome approximations, such as Taj-s
 
 Use `RectRing` for rectangular ring bands around an open interior: eave bands on tiered towers and pagoda-style roofs, cornices, parapets, plinth bands, balcony fascias, and trim frames around courtyards or roof plates. It is the rectangular counterpart to `CircleRing` and expands into at most four axis-aligned band boxes (`ring_front`, `ring_back`, `ring_left`, `ring_right`) inside one anchored bounding box. Use `options.bandWidth` for the inward band thickness and `options.height` for the band height. The band must leave at least a one-block open interior; use `Platform` instead when the surface should be a full slab. Pair it with `SteppedDome` or `CircleRing` for curved caps.
 
+Use `EllipseRing` for bounded oval shells, arenas, courtyards, and curved walls that need true ellipse curvature rather than a stadium approximation. Its integer `placement.center`, `radiusX`, and `radiusZ` define the ellipse on XZ; `placement.y` is the base layer. `options.height` and `options.thickness` default to 1, and `options.fill` defaults to `hollow`. Hollow rings subtract an inner ellipse inset by the thickness on both axes. Optional `startAngle`/`endAngle` select a partial ellipse using the same 0° (+X), increasing-toward-+Z convention as `CircleRing`. Bounds validation uses the full declared ellipse, including for a partial arc. Expansion emits deterministic single-block `SolidBox` nodes and keeps ordinary material, provenance, and support analysis behavior.
+
+Use `PathRepeat` to place one reusable assembly at count-based samples along an ellipse, such as arcade bays or colonnade modules. The source is an assembly ID. `placement.y` is a non-negative logical height offset applied globally to every repeated sample as `y * grid.unitBlocks`; assembly member Y coordinates stay local and unchanged. The path point aligns with the XZ center of the assembly bounds, rounded to the nearest voxel when the pivot falls between blocks. `orientToTangent: true` rotates local +X onto the analytic ellipse tangent and uses the existing deterministic integer voxel rotation. It defaults to `false`. The schema is intentionally ellipse-only:
+
+```json
+{
+  "id": "arcade_bays",
+  "type": "PathRepeat",
+  "placement": {
+    "path": { "type": "ellipse", "center": { "x": 36, "z": 20 }, "radiusX": 25, "radiusZ": 13 },
+    "source": "bay_module",
+    "count": 24,
+    "y": 0,
+    "startAngle": 0,
+    "endAngle": 360,
+    "closed": true,
+    "orientToTangent": true
+  }
+}
+```
+
+Closed paths emit `count` samples over one full turn without a duplicate seam endpoint. Use equal `startAngle` and `endAngle` values to choose a phase (for example, `7.5` to `7.5`); the legacy `0` to `360` form remains valid. Open paths require at least two samples over a non-zero sweep and include both endpoints. If `endAngle` is less than `startAngle` on an open path, sampling continues forward through 360°. Angles use the ellipse parameterization `x=cx+radiusX*cos(t)`, `z=cz+radiusZ*sin(t)`. The declared ellipse, Y-shifted rotated assembly envelope, and every emitted voxel must fit the plan bounds. Block budgeting conservatively sums each rotated source-assembly bounds envelope per sample without discounting overlap; vertical placement does not reduce that estimate. `PathRepeat` supports assemblies only; use `Instance` for one-off placements. It does not support arc-length spacing or general curves.
+
 For stepped eave curvature, set `options.cornerRise` to a small non-negative integer: each corner column gains up to that many extra blocks above `options.height`, stepping down over `options.riseSpan` columns (defaults to `cornerRise`, one block per step) toward the middle of each edge. This approximates curved eave edges and corner uplift with deterministic integer segments named `ring_<side>_seg<n>`; keep the ring's inner hole aligned with the tower cross-section at that height so the band bears on the walls. The placement must declare vertical room (`options.height + options.cornerRise <= placement.size.height`) or validation rejects the plan. Flat rings without `cornerRise` expand exactly as before. Components that consume a cornerRise ring through `inputs` are connected to every emitted segment, preserving whole-ring bearing in the expanded graph.
 
 Use `RailingRun` for repeated posts plus horizontal rails along bridges, decks, walls, balconies, and platforms. It is a bounded run, not a fence/pathfinding simulator. Use `postSpacing`, `includeTopRail`, and `includeMidRail` for controlled detail.

docs/LLM_AUTHORING_CONTRACT.md

@@ -122,6 +122,10 @@ Use `RailingRun` for bounded posts and rails along decks, bridges, walls, and ba
 
 Use `RectRing` for rectangular eave bands, cornices, parapets, plinth bands, and trim frames with an open interior. Set `options.bandWidth` for band thickness; keep at least a one-block open hole. Use `Platform` for full slabs and `CircleRing` for circular rings. For pagoda/temple eaves, set `options.cornerRise` (1-3) with `options.riseSpan` (defaults to `cornerRise`) so the band steps upward toward each corner, approximating curved eave edges and corner uplift; size the ring so its inner hole matches the wall cross-section at that height, and give the placement enough height for base + rise. Do not invent pagoda-eave or landmark-specific ring types. Components that declare `inputs` on a cornerRise ring are automatically attached to every emitted segment, so no per-segment refs are needed.
 
+Use `EllipseRing` for true oval shells and curved walls. Set `placement.center`, `radiusX`, and `radiusZ`; use `options.height` and `options.thickness` for a hollow wall. It uses a deterministic voxel ellipse, not two circular caps and tangent walls. Partial `startAngle`/`endAngle` use the `CircleRing` angle convention, and bounds must contain the full declared ellipse.
+
+Use `PathRepeat` for a reusable assembly repeated along an ellipse, such as a curved arcade. Set `placement.path` to `{ "type": "ellipse", "center": { "x": ..., "z": ... }, "radiusX": ..., "radiusZ": ... }`, then set `source`, `count`, non-negative integer `y`, `startAngle`, `endAngle`, and `closed`. `y` shifts every sample globally by `y * grid.unitBlocks`; keep Y coordinates in the reusable assembly local so the same module can be repeated at multiple levels. Closed paths use `count` samples without a duplicate seam endpoint; equal start/end angles set the phase of the full loop (legacy `0` to `360` is also accepted). Open paths include both endpoints and need at least two samples. Set `orientToTangent: true` to align assembly local +X to the ellipse tangent. The declared shifted assembly envelope and every rotated voxel must fit plan bounds. This is count-based ellipse sampling, not arc-length spacing or a generic curve language.
+
 Use `ArcadeRun` for repeated stepped arch-like facade rhythms: colosseum bays, gothic arcades, palace cloisters, bridge arches, and monumental walls. Do not try to describe exact curves; use Minecraft-like blocky arches.
 
 Use `SupportBracket` for visible support under overhangs, balconies, lifeboat shelves, awnings, and light bridge edges. Pair it with `structural.maxCantilever` when the bracket is intended to satisfy support diagnostics. Do not use it to silence unrelated floating structures.

docs/llm.txt

@@ -23,7 +23,7 @@ Authoring rules
 10. If validation fails, repair the plan instead of loosening schema or validation.
 
 Allowed ComponentPlan components
-Foundation, Platform, Beam, RoomShell, Compartment, Corridor, StairRun, FloorStack, TaperedVolume, SteppedTier, VerticalSetbackVolume, SteppedDome, RailingRun, ArcadeRun, SupportBracket, TreeCanopy, OrganicPatch, PathRun, RockCluster, Light, Door, Window, Opening, Portal, GableRoof, FlatRoof, SupportPost, Repeat, Instance.
+Foundation, Platform, Beam, RoomShell, Compartment, Corridor, StairRun, FloorStack, TaperedVolume, SteppedTier, VerticalSetbackVolume, SteppedDome, RectRing, EllipseRing, PathRepeat, RailingRun, ArcadeRun, SupportBracket, TreeCanopy, OrganicPatch, PathRun, RockCluster, Light, Door, Window, Opening, Portal, GableRoof, FlatRoof, SupportPost, Repeat, Instance.
 
 When to use key components
 - RoomShell: one exterior or interior hollow volume.
@@ -36,6 +36,8 @@ When to use key components
 - SteppedTier: pyramids, amphitheater seating, podiums, terraces.
 - VerticalSetbackVolume: tall towers, pagodas, skyscrapers, spires.
 - SteppedDome: Minecraft-style dome roofs and caps.
+- EllipseRing: true bounded oval shell using integer center and radii.
+- PathRepeat: count-based ellipse path for a reusable assembly; non-negative integer `placement.y` globally offsets local assembly Y, closed paths omit the seam and allow phase with equal start/end angles, open paths include both endpoints, and orientToTangent aligns local +X.
 - ArcadeRun: repeated blocky arches in facades or bridges.
 - SupportBracket: visible supports under overhangs, balconies, lifeboat shelves.
 - TreeCanopy, OrganicPatch, PathRun, RockCluster: landscape and garden detail.