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/lang/lifecycle.ludic

@@ -0,0 +1,28 @@
+# lifecycle.ludic — a game's whole lifecycle as @-hooks. Each fires at one point
+# on the timeline and reduces to ordinary code, so nothing is hidden and the
+# data-oriented model is untouched. Running it prints: 1 700 50 950 2 — one line
+# per hook, in the order the timeline reaches them.
+#
+#   boot ── @OnStart ──▶ spawn ── @OnAttach, @OnSpawn ──▶ … ── @OnDespawn ──▶ quit ── @OnQuit
+program Life {
+  property Health { hp: int = 0, max: int = 100 }
+  property Sprite { id: int = 0 }
+  model Enemy { Health, Sprite }
+
+  # ---- program lifecycle -----------------------------------------------------
+  @OnStart handler Boot { print(1) }               # once, at boot
+  @OnQuit  handler Bye  { print(2) }               # once, at shutdown
+
+  # ---- property / entity lifecycle -------------------------------------------
+  @OnAttach(Sprite)  handler Load  { print(Sprite.id + 700) }   # when a Sprite is attached
+  @OnSpawn(Enemy)    handler Init  { Health.hp = Health.max }        # constructor
+  @OnDespawn(Enemy)  handler Clean { print(Health.hp + 900) }    # destructor (dispatched by kind)
+
+  handler Seed phase Start { spawn Enemy { Health { max: 50 } } }
+
+  handler Run phase Render {
+    for (h) in query [Health] { print(h.hp) }      # 50 — Init set hp to max
+    for (e) in query [Health] { despawn self() }        # Clean fires: 50 + 900 = 950
+    quit()
+  }
+}