Raw x/y arguments are interpreted in the most recent screenshot's pixel
space and auto-scaled to device coordinates via screenshotScaleMap (set
when screen_capture is called with maxWidth/maxHeight smaller than the
device resolution). This is documented in code (`applyScale` helper) but
NOT in tool descriptions or README, leading to surprises:

  - "tap(415, 820)" producing "tap(2075, 4220)" because the last
    screenshot was at preset='low' on a 1080-wide device (5× scale).
  - Confusion between coords reported by ui_find / ui_tree (which are
    device coords from uiautomator) vs raw x/y (screenshot coords) —
    passing the former as the latter when a low-res screenshot is the
    most recent capture causes silent over-scaling.

Updates:
- input_tap top-level description now spells out the coord-space rule,
  the "no screenshot taken yet" fallback (1× scale), and the ui_*-vs-raw
  pitfall. Recommends using index/text/resource...