feat(pixel-art): add hardware palettes and video animation (#12725)

Expand the pixel-art skill from 2 presets (arcade, snes) to 14 presets
with hardware-accurate palettes (NES, Game Boy, PICO-8, C64, Apple II,
MS Paint, CRT mono), plus a procedural video overlay pipeline.

Ported from Synero/pixel-art-studio (MIT). Full attribution in
ATTRIBUTION.md.

What's in:
- scripts/palettes.py — 28 named RGB palettes (hardware + artistic)
- scripts/pixel_art.py — 14 presets, named palette support, CLI
- scripts/pixel_art_video.py — 12 animation scenes (stars, rain,
  fireflies, snow, embers, lightning, etc.) → MP4/GIF via ffmpeg
- references/palettes.md — palette catalog
- SKILL.md — clarify-tool workflow (offer style, then optional scene)

What's out (intentional):
- Wu's quantizer (PIL's built-in quantize suffices)
- Sobel edge-aware downsample (scipy dep not worth it)
- Atkinson/Bayer dither (would need numpy reimpl)
- Pollinations text-to-image (Hermes uses image_generate instead)

Video pipeline uses subprocess.run with check=True (replaces os.system)
and tempfile.TemporaryDirectory (replaces manual cleanup).

skills/creative/pixel-art/ATTRIBUTION.md

@@ -0,0 +1,54 @@
+# Attribution
+
+This skill bundles code ported from a third-party MIT-licensed project.
+All reuse is credited here.
+
+## pixel-art-studio (Synero)
+
+- Source: https://github.com/Synero/pixel-art-studio
+- License: MIT
+- Copyright: © Synero, MIT-licensed contributors
+
+### What was ported
+
+**`scripts/palettes.py`** — the `PALETTES` dict containing 23 named RGB
+palettes (hardware and artistic). Values are reproduced verbatim from
+`scripts/pixelart.py` of pixel-art-studio.
+
+**`scripts/pixel_art_video.py`** — the 12 procedural animation init/draw pairs
+(`stars`, `fireflies`, `leaves`, `dust_motes`, `sparkles`, `rain`,
+`lightning`, `bubbles`, `embers`, `snowflakes`, `neon_pulse`, `heat_shimmer`)
+and the `SCENES` → layer mapping. Ported from `scripts/pixelart_video.py`
+with minor refactors:
+- Names prefixed with `_` for private helpers (`_px`, `_pixel_cross`)
+- `SCENE_ANIMATIONS` renamed to `SCENES` and restructured to hold layer
+  names (strings) instead of function-name strings resolved via `globals()`
+- `generate_video()` split: the Pollinations text-to-image call was removed
+  (Hermes uses its own `image_generate` + `pixel_art()` pipeline for base
+  frames). Only the overlay + ffmpeg encoding remains.
+- Frame directory is now a `tempfile.TemporaryDirectory` instead of
+  hand-managed cleanup.
+- `ffmpeg` invocation switched from `os.system` to `subprocess.run(check=True)`
+  for safety.
+
+### What was NOT ported
+
+- Wu's Color Quantization (PIL's built-in `quantize` suffices)
+- Sobel edge-aware downsampling (requires scipy; not worth the dep)
+- Bayer / Atkinson dither (would need numpy reimplementation; kept scope tight)
+- Pollinations text-to-image generation (`pixelart_image.py`,
+  `generate_base()` in `pixelart_video.py`) — Hermes has `image_generate`
+
+### License compatibility
+
+pixel-art-studio ships under the MIT License, which permits redistribution
+with attribution. This skill preserves the original copyright notice here
+and in the SKILL.md credits block. No code was relicensed.
+
+---
+
+## pixel-art skill itself
+
+- License: MIT (inherits from hermes-agent repo)
+- Original author of the skill shell: dodo-reach
+- Expansion with palettes + video: Hermes Agent contributors