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/toggle.ludic

@@ -1,37 +0,0 @@
-# toggle.ludic — enable/disable at the three ECS scopes, each a plain statement.
-# Disabling never destroys data: a property's values persist in storage, so a
-# later `enable` restores them. Queries already skip a cleared flag, so nothing
-# else in the language needs to know. Running it prints: 6 0 7 1 0
-#
-#   disable P on e   clears one entity's has-flag   (@OnDisable / @OnEnable fire)
-#   disable Model    flips the model's enabled flag (its entities drop from queries)
-#   disable Handler  flips the handler's enabled flag (it stops running each phase)
-program Toggles {
-  property Health { hp: int = 0, max: int = 100 }
-  property Shield { amount: int = 0 }
-  model Player { Health, Shield }
-
-  # hooks run at the toggle point with the property's data bound by name
-  @OnDisable(Shield) handler Down { print(Shield.amount + 1) }   # 5 + 1
-  @OnEnable(Shield)  handler Up   { print(Shield.amount + 2) }   # 5 + 2
-
-  handler Seed phase Start { spawn Player { Health { max: 50 }, Shield { amount: 5 } } }
-
-  handler Run phase Render {
-    for (e) in query [Player] { disable Shield on self() }   # @OnDisable -> 6
-    var n = 0
-    for (s) in query [Shield] { n += 1 }
-    print(n)                                             # 0 — no live Shield now
-
-    for (e) in query [Player] { enable Shield on self() }    # @OnEnable -> 7, data intact
-    n = 0
-    for (s) in query [Shield] { n += 1 }
-    print(n)                                             # 1 — amount is still 5
-
-    disable Player                                           # whole model off
-    n = 0
-    for (p) in query [Player] { n += 1 }
-    print(n)                                             # 0 — model disabled
-    quit()
-  }
-}