chore(repo): DX cleanup — categorise examples, text-diffable golden, build/ output (#27 #28 #30)

Repository-cleanup / DX pass folding three tracker items into one coherent
change, verified green end to end (`bin/x test` 49/0, `bin/x selfhost-test`
29/0, `bin/x test-tools` 29/0).

#28 — curate & categorise examples/
- 42 flat entries regrouped into intent-revealing subdirs: games/, rendering/,
  ecs/, events/, networking/, lang/, library/ (was lib/).
- chronorift dir-vs-file duplication resolved: the entry file and its import
  modules now live together under games/chronorift(.ludic).
- Every path reference updated repo-wide (test runner, editor-tool drivers,
  docs/site, design docs).
- New examples/README.md indexes the whole set with run commands.
- Showcase examples without a self-asserting entry (hello, events, net_rt) now
  get a compile-only rot guard in `bin/x test`, so nothing here rots silently.

#30 — text-diffable golden baseline
- The 4 binary selfhost/golden/*.ppm blobs are replaced by a single
  selfhost/golden/renders.sha256 manifest (SHA-256 per render). Hashes are
  byte-identical to the old PPMs, so the baseline is unchanged — only its form.
- game_case now compares framebuffer hashes; a regression shows as a changed
  hex line in review, not "binary files differ".
- New `bin/x golden` regenerates the manifest deliberately (review with
  `git diff selfhost/golden/renders.sha256`).

#27 — PPM & asset handling
- Headless renders now write build/out.ppm, never the repo root; `x app`,
  `x clean`, messaging and .gitignore updated to match. Nothing is written to
  the working root any more.
- Redundant local Kenney .zip archives removed (the art ships extracted;
  .gitignore already excludes *.zip). CC0 License.txt files retained.

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

examples/README.md

@@ -0,0 +1,101 @@
+# Examples
+
+A curated tour of Ludic, grouped by intent. Every example here is exercised by
+the test suite (`bin/x test` / `bin/x selfhost-test`), so nothing in this
+directory silently rots.
+
+Run any program straight from the repository root (so `assets/` resolves):
+
+```sh
+bin/x app examples/games/snake.ludic              # compile + open a real window
+bin/x app examples/games/snake.ludic --headless   # render one frame to build/out.ppm
+bin/ludic examples/lang/offline_rewards.ludic     # compile + run a plain program
+```
+
+## `games/` — complete, windowed games
+
+| Example | What it shows |
+|---|---|
+| [`games/snake.ludic`](games/snake.ludic) | A full game from primitives: input, grid, growth, collision, score. |
+| [`games/menu.ludic`](games/menu.ludic) | A retained-UI title screen — the UI declared as data. |
+| [`games/chronorift.ludic`](games/chronorift.ludic) | A 2D co-op JRPG: overworld, dungeon, random encounters, turn battle, boss, save. The entry file `import`s the modules under [`games/chronorift/`](games/chronorift/). |
+
+## `rendering/` — drawing primitives
+
+| Example | What it shows |
+|---|---|
+| [`rendering/draw_prims.ludic`](rendering/draw_prims.ludic) | The extended `Screen.*` primitives — line, circle, triangle, fill, sprite. |
+
+## `ecs/` — the entity-component world
+
+| Example | What it shows |
+|---|---|
+| [`ecs/hello.ludic`](ecs/hello.ludic) | The smallest program that exercises the ECS pipeline. |
+| [`ecs/world_get.ludic`](ecs/world_get.ludic) | Reflection: read/write a component by name. |
+| [`ecs/world_scan.ludic`](ecs/world_scan.ludic) | Reflection: scan the world and identify each entity. |
+| [`ecs/world_query.ludic`](ecs/world_query.ludic) | Reflection: iterate the world by property. |
+| [`ecs/world_spawn.ludic`](ecs/world_spawn.ludic) | Reflection: a mod spawns a fresh entity by model id. |
+| [`ecs/world_mixed.ludic`](ecs/world_mixed.ludic) | Reflection: get/set through real struct offsets. |
+| [`ecs/world_dyn.ludic`](ecs/world_dyn.ludic) | Reflection: register a brand-new component at runtime. |
+
+## `events/` — the event bus
+
+| Example | What it shows |
+|---|---|
+| [`events/events.ludic`](events/events.ludic) | EV0: the event-bus core — declare, `emit`, `@On`. |
+| [`events/mod_events.ludic`](events/mod_events.ludic) | Two listeners on one event, driven from a mod. |
+| [`events/cancel.ludic`](events/cancel.ludic) | EV3: cancellable (decision) events. |
+| [`events/recurse.ludic`](events/recurse.ludic) | EV6: re-entrant `emit` is depth-bounded — no runaway cycle. |
+| [`events/promote.ludic`](events/promote.ludic) | EV1: `@Public` promotes a lifecycle hook to a public event. |
+| [`events/prop_events.ludic`](events/prop_events.ludic) | EV1 for properties: attach/detach events. |
+| [`events/scene_events.ludic`](events/scene_events.ludic) | EV1 for scenes: on-enter / on-exit events. |
+| [`events/program_events.ludic`](events/program_events.ludic) | EV1 for the program scope: start/quit events. |
+| [`events/layer_events.ludic`](events/layer_events.ludic) | EV1 for layers + a `public` layer's show/hide events. |
+| [`events/scoped.ludic`](events/scoped.ludic) | A despawned entity drops out of subsequent event work. |
+
+## `networking/` — deterministic multiplayer (N0–N6)
+
+Each maps to a stage of [`NETWORKING-DESIGN.md`](../NETWORKING-DESIGN.md); all run
+over the compiler's built-in loopback transport with zero foreign code.
+
+| Example | What it shows |
+|---|---|
+| [`networking/net_echo.ludic`](networking/net_echo.ludic) | N0: the transport seam. |
+| [`networking/net_snapshot.ludic`](networking/net_snapshot.ludic) | N1: whole-world snapshot to a memory buffer. |
+| [`networking/net_sync.ludic`](networking/net_sync.ludic) | N2: `@Sync` replication codegen. |
+| [`networking/net_owner.ludic`](networking/net_owner.ludic) | N3: entity ownership. |
+| [`networking/net_rpc.ludic`](networking/net_rpc.ludic) | N4: remote events / RPCs. |
+| [`networking/net_roles.ludic`](networking/net_roles.ludic) | N5: handler roles + the drivable sim. |
+| [`networking/net_demo.ludic`](networking/net_demo.ludic) | N6: a networked game end to end, in pure Ludic. |
+| [`networking/net_rt.ludic`](networking/net_rt.ludic) | A blessed server-authoritative replication runtime. |
+
+## `lang/` — language & standard-library tour
+
+| Example | What it shows |
+|---|---|
+| [`lang/annotations.ludic`](lang/annotations.ludic) | The annotation-first style: `@Queries` / `@Computed` / `@OnSpawn` / `@Handles`. |
+| [`lang/qdecl.ludic`](lang/qdecl.ludic) | `@Queries` desugaring to the query system. |
+| [`lang/lifecycle.ludic`](lang/lifecycle.ludic) | The whole game lifecycle as `@`-hooks, in firing order. |
+| [`lang/detach.ludic`](lang/detach.ludic) | Structural attach/detach + `@OnAttach` / `@OnDetach`. |
+| [`lang/reason.ludic`](lang/reason.ludic) | Reason-carrying teardown (`@OnDespawn`: Despawned vs Quit). |
+| [`lang/toggle.ludic`](lang/toggle.ludic) | enable/disable at the three ECS scopes. |
+| [`lang/scenes.ludic`](lang/scenes.ludic) | One active scene at a time, handlers grouped into layers. |
+| [`lang/strings.ludic`](lang/strings.ludic) | Strings as values: compare, join, interpolate, slice. |
+| [`lang/rng_demo.ludic`](lang/rng_demo.ludic) | The `Random.*` extensions (value/int/sign). |
+| [`lang/time_demo.ludic`](lang/time_demo.ludic) | `Time.frame` / `elapsed` / `delta`. |
+| [`lang/offline_rewards.ludic`](lang/offline_rewards.ludic) | A worked idle-game example over the Time/Date/Duration stdlib. |
+
+## `library/` — building and linking a shared library
+
+A how-to for compiling a `.ludic` module to a native `.dylib`/`.so`/`.dll` and
+linking a second program against it via `extern fn`:
+
+```sh
+bin/ludicc examples/library/combat.ludic --shared -o build/libcombat.dylib
+bin/ludicc examples/library/arena.ludic  -o build/arena -Lbuild -lcombat
+```
+
+| Example | What it shows |
+|---|---|
+| [`library/combat.ludic`](library/combat.ludic) | Exported functions callable across the C ABI. |
+| [`library/arena.ludic`](library/arena.ludic) | A program that links against the shared library. |