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>

README.md

@@ -730,6 +730,7 @@ GM_STEPS=20 node tools/e2e.mjs                                # or 1-12, or 6,20
 ./e2e.sh status                                               # live progress, or the last run's result
 node tools/seed-jumprun.mjs && node tools/smoke-jumprun.mjs   # 24 checks: the example game, played end to end
 node tools/seed-tetris.mjs && node tools/smoke-tetris.mjs     # 19 checks: the Tetris example, played end to end
+node tools/seed-actor.mjs && node tools/smoke-actor.mjs       # 19 checks: the walk demo (the seed uploads its own sheet)
 ```
 
 **A run needs a working GPU.** An idle editor page keeps rendering a picture that never changes, and
@@ -849,6 +850,21 @@ no loop and no list access of its own, which `tools/smoke-tetris.mjs` checks. Th
 the game in a headless browser (fall, move, turn, drop, land, clear a line, fill the well) – it
 is the regression test for loops, lists and behaviors used as nodes.
 
+**The walk demo** (`tools/seed-actor.mjs`, project *Actor demo*) is the smallest of the three and the
+only one that ships its own picture: it uploads `tools/assets/Actor1.png` and slices the 576×384
+sheet into the 96 cells of a 12×8 grid. That is the usual RPG-Maker layout – eight characters, each
+three columns (left foot / standing / right foot) by four rows (down, left, right, up) – and the demo
+wears the one in the top left corner. Walking is four **ping-pong** animations of three frames, which
+is exactly the original walk cycle; standing is no animation at all but the middle frame of the row.
+The graph builds what the sprite wears **by name**, pasting `walk-` or `idle-` in front of the
+direction it faces, which is why the standing frames carry named ids. Which way it looks is the key
+pressed last, corrected whenever only one axis is held – otherwise letting go of one key of a
+diagonal would leave it walking backwards. It is the worked example for animations, for a seed that
+brings its own texture, and for `Axis input`, whose vector is already normalized so a diagonal is not
+faster than a straight line. `tools/smoke-actor.mjs` walks it in a headless browser; that the
+animation really advances it reads off the **drawn pixels**, standing at the edge of the camera where
+he walks on the spot – a clock that ticks without the picture following would pass otherwise.
+
 The workspace folder itself is what nginx serves, so `npm run build` is the deployment.
 
 ## API