Add a four-direction walk demo that seeds its own sprite sheet

tools/seed-actor.mjs builds the project Actor demo: it uploads
tools/assets/Actor1.png, slices the 576x384 sheet into the 96 cells of a
12x8 grid (48x48 each, no remainder) and wears the character in the top
left corner. Walking is four ping-pong animations of three frames, which
is the original RPG-Maker walk cycle; standing is the middle frame of the
row, not an animation.

The graph pastes walk- or idle- in front of the direction faced and wears
the result, so eight cases need no branch tree - the List node only holds
numbers. Which way it looks is the key pressed last, corrected whenever
only one axis is still held, or letting go of one key of a diagonal would
walk backwards. Axis input already normalizes its vector.

tools/lib/projects.mjs gains uploadTexture, since data/textures/ is
git-ignored and a seed that ships its picture has to send it. The harness
gains w/a/s/d and keyDown/keyUp halves, because holdKey cannot express two
presses that overlap - which is what a diagonal is.

tools/smoke-actor.mjs plays it in 19 checks and reads the drawn pixels at
the camera edge, where the bounds hold him walking on the spot: three
distinct frames walking, one standing.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

tools/lib/projects.mjs

@@ -6,14 +6,19 @@
  *   fixture     rewritten by every e2e run (tools/seed-e2e.mjs + tools/e2e.mjs).
  *   jumpRun     the example game (tools/seed-jumprun.mjs, played by tools/smoke-jumprun.mjs).
  *   tetris      the second example game (tools/seed-tetris.mjs, played by tools/smoke-tetris.mjs).
+ *   actor       the four-direction walk demo (tools/seed-actor.mjs).
  *
  * All ids exist on the server (created via POST ?r=projects); PUT does not create projects.
  */
+import { readFile } from 'node:fs/promises';
+import { extname } from 'node:path';
+
 export const PROJECTS = {
   playground: '649188c15414',
   fixture: '3caa9b6a0c92',
   jumpRun: '3d271f3bb58b',
   tetris: '2072b56583af',
+  actor: '3ccb5c67220b',
 };
 
 export const DEFAULT_BASE_URL = 'https://nockal.com/game-maker/';
@@ -32,6 +37,40 @@ export function cliArgs(script, defaultId) {
   return { projectId, baseUrl };
 }
 
+const MIME = {
+  png: 'image/png',
+  jpg: 'image/jpeg',
+  jpeg: 'image/jpeg',
+  webp: 'image/webp',
+  gif: 'image/gif',
+};
+
+/**
+ * Uploads an image and returns `{file, width, height}` for a texture asset. Storage is
+ * content-addressed, so re-seeding the same file is a no-op rather than a second copy – which is
+ * what makes a seed that ships its own image reproducible (`data/textures/` is git-ignored).
+ */
+export async function uploadTexture(baseUrl, filePath) {
+  const bytes = await readFile(filePath);
+  const type = MIME[extname(filePath).slice(1).toLowerCase()];
+  if (!type) {
+    console.error(`unsupported image type: ${filePath}`);
+    process.exit(1);
+  }
+  const res = await fetch(`${baseUrl}api/index.php?r=textures`, {
+    method: 'POST',
+    headers: { 'Content-Type': type },
+    body: bytes,
+    signal: AbortSignal.timeout(20_000),
+  });
+  const result = await res.json();
+  if (!res.ok) {
+    console.error('texture upload failed', res.status, result);
+    process.exit(1);
+  }
+  return { file: result.file, width: result.width, height: result.height };
+}
+
 /** Overwrites a project, keeping the name it already has on the server. */
 export async function writeProject(projectId, baseUrl, project) {
   const url = `${baseUrl}api/index.php?r=projects/${projectId}`;