feat(stdlib): Tiled P4 — objects, custom props/types, templates, opt-in spawn (#72)

- Object layers: all shapes (rectangle/ellipse/point/polygon/polyline/text) and
  custom properties parse and are queryable — Tiled.object_count / Tiled.object /
  Tiled.object_shape, and Tiled.prop / prop_int / prop_type over any object /
  tile / layer / map.
- Custom types: Tiled.load_types reads an objecttypes.xml project custom-type
  table so a class property resolves its default; enum values resolve as strings.
- Templates: Tiled.template reads a .tx/.tj, and Tiled.load merges each object's
  `template` reference under the instance's overrides (field inheritance).
- Opt-in spawning: Tiled.spawn / Tiled.spawn_layer map an object's class +
  properties onto Ludic components through the reflection ABI (Position from x/y,
  each property to a like-named field). Off by default — no gameplay coupling in
  the core load. Split into tiled_spawn.ludic, spliced only for a Tiled *game*
  (the world table exists only under has_ecs), so a plain map-reading tool never
  links against the reflection ABI.

Proven by library/tiled_p4.ludic (18 assertions) incl. the design's named
orthogonal-outside.tmx object shapes. x test: 95 passed.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

changes/tiled-maps.md

@@ -8,3 +8,4 @@ type: feat
 - **P1 core load + render (#69)** — the runtime `rt_tmap` model (heap-allocated to `w·h`, lifting the old `96×64` cap), the GID resolver (`Tiled.resolve` → tileset / local id / H·V·D flips), image-backed rendering (`Tiled.draw`, flips applied at blit), and the legacy-tilemap compatibility projection so `Grid.*`/`Path.*`/`esys_move` keep working. `Tiled.load` reads either format, resolves external tilesets + images, and auto-projects a `collision` layer. The Kenney sample loads and renders pixel-identically from `.tmx` and `.tmj`; the `grid` and `physics_tiles` demos now run off a loaded map.
 - **P2 collision & grid (#70)** — normalise three collision sources into the byte tilemap `esys_move`/`Grid.*`/`Path.*` read, in the design's priority order: per-tile `<objectgroup>` hitboxes, the `solid`/`oneway`/`trigger` property convention (`Tiled.collision_kind`/`Tiled.tile_shapes`), and the designated collision layer (`Tiled.project`, any non-zero GID solid) — or drive collision from a visual layer's per-tile metadata alone (`Tiled.collide`). The property convention and the collision-layer fallback produce the same feed; `Path.a_star` over a loaded map matches the hand-authored baseline.
 - **P3 animated tiles + tile objects (#71)** — a tileset `<animation>` advances deterministically as a pure function of the fixed 60/s engine frame clock (`Tiled.frame_gid`/`Tiled.animated`), so an animated GID resolves at draw to the current frame's GID with its flip flags preserved and reproduces frame-for-frame across runs; `Tiled.draw_anim` draws a map with animations advanced. Object-layer entries with a `gid` render the tile image (with their own flips), bottom-anchored, as placeable sprites.
+- **P4 objects, properties, templates, spawning (#72)** — all object shapes (rectangle / ellipse / point / polygon / polyline / text) and custom properties parse and are queryable (`Tiled.object`, `Tiled.object_shape`, `Tiled.prop`/`Tiled.prop_int`/`Tiled.prop_type`); class properties resolve their defaults against a project custom-type table (`Tiled.load_types` over `objecttypes.xml`); template instances inherit their `.tx`/`.tj` template's fields; and an object maps onto Ludic components on demand (`Tiled.spawn`/`Tiled.spawn_layer`, off by default, via the reflection ABI).