Ink Wash

Make a video in the Ink Wash style from ultramotion.ai: https://ultramotion.ai/styles/ink-wash/
The style is an open-source Agent Skill. If you can install skills, run npx skills add sunsiyuan/ultramotion first and build it with the ink-wash template (ink.js paints ink that spreads on rice paper, render.py renders, sound.py makes the sound). If you can't, write it from scratch following the description below.

[Deliverable]
- Subject: misty spring rain in Jiangnan, Chinese ink painting.
- Vertical 1080×1920, 30 fps, 18 seconds, an mp4 with music, saved in the current directory.
- Every frame is a pure function of time t, all randomness seeded; render with a headless browser frame by frame, encode with ffmpeg, then add the music.

[Get the painting first]
- If you can generate images (any image tool), generate a vertical ink-wash landscape: Jiangnan in misty rain, three layers of mountains paling into the distance, the near ones in rich dark ink with texture strokes and moss dots; white-walled houses with dark roofs and willows half hidden in mist on the left; the lower half a wide empty river with a few faint ink lines; open sky above. Five tones of ink, a touch of pale green on the willows only. No text, seal, boats, people or birds in it — those are animated.
- If you can't, build it from ink layers: three ranges, the houses, willows, river lines.

[How ink reaches the paper]
- Ink is not paint: each layer has a map of how much ink and a map of when it arrives. Ink creeps out from where the brush touched, darker at its wet front, a little lighter once dry. Everything adds up as density and the paper absorbs light through it (paper × e^(−density)), so the five tones come out by themselves.
- The painting spreads from mid-mountain (about 260, 620): the dark bones arrive first, the pale washes after; it is all there by about 4 s.

[The picture is alive the whole time — this is the style]
- Laying the ink down is only the first few seconds; until the last frame something keeps moving:
  - From 4.5 s, fine rain slants down and the drops ring the river.
  - Two bands of mist drift sideways, thinning the ink as they pass.
  - From 6.5 s, a small covered boat crosses the river slowly from right to left, the boatman in a straw hat working the oar, a faint wake behind.
  - The camera pushes in slowly the whole time.
- A large emptiness, one small life: half the frame or more is paper and mist; one small thing really moves.

[Title and seal]
- At 12.5 s, a vertical title in running script top right, "烟雨", brushed in one character at a time, with a small line of verse beside it, "多少楼台烟雨中".
- At 15.6 s a white-text seal "江南": seal script carved out of a red block, the two characters right to left, stretched to fill the square; uneven paste, specks of bare paper, chipped corners; a small press as it lands.

[Sound]
- Synthesize the music in code: a pentatonic pluck (guzheng feel) on D, one note every 1.3 s, over a long pad; from 4.5 s a 13-second wash of wind and rain; a soft thud as the seal lands.

[Check before you hand it over]
- Look at a contact sheet: once the ink is down, is something still moving? A painting that holds still is a slideshow.
- A row of identical triangles: vary the mountains — rounded, jagged, flat-topped, a single peak, different heights and widths.
- Everything one grey: distant pale, near dense.
- Too busy: remove things until half the frame is paper.