refactor(skill): 主技能 subskill 目录更名 subskills（09-02 用户要求）

- V1.0/subskill/ → V1.0/subskills/（browser-harness/mcn-dou-analysis/mcn-script-review/mcn-video-prompt，git 识别 R100 纯重命名保留历史）
- 路径说明同步：V1.0/SKILL.md（96/105行）、Lite1.0/SKILL.md（66行）、mcn-dou-analysis/SKILL.md 红线行、操作规范.md 159/175行、mcn-work-shop app.js SKILL_HINT_ACCOUNT
- 用户环境 ~/.workbuddy/skills/短视频脚本创作/ 与源仓库 V1.0 同 inode（junction），自动同步无需单独改
- mcn-dou-analysis 内部 subskills/nuwa-skill-main 为正常结构不受影响

project/短视频脚本创作/V1.0/subskills/browser-harness/interaction-skills/screenshots.md

@@ -0,0 +1,17 @@
+# Screenshots
+
+`capture_screenshot()` writes a PNG of the current viewport. The file is in **device pixels** — on a 2× display a 2296×1143 CSS viewport produces a 4592×2286 PNG.
+
+That matters for two reasons:
+
+1. **Click coordinates are CSS pixels.** Don't read a target off the image and pass it to `click_at_xy()` directly without dividing by `devicePixelRatio`. The simplest workflow is to take the screenshot, look at it in a viewer that shows CSS coordinates, or measure relative positions and use `js("window.devicePixelRatio")` to convert.
+
+2. **Some LLMs reject images > 2000 px per side.** Long sessions on 2× displays will eventually hit this. Pass `max_dim=1800` to downscale the file before it gets into the conversation:
+
+```python
+capture_screenshot("/tmp/shot.png", max_dim=1800)
+```
+
+The downscale only happens when the image actually exceeds `max_dim`, so it's safe to leave on for every shot.
+
+Use full-page screenshots (`full=True`) only when you need to see content below the fold — they are much larger and slower than viewport-only.