0.9.0 — vocabulary 19: pixel mode, an arcade HUD and a news ticker

Pixel mode, an arcade HUD and a news ticker: palette-exact whole-pixel drawing (spec 026,
#111, #158, #159), the data-bound versus-bars and hud-score (spec 027, #105, #106), and
ticker (#139). No existing reference frame moved.

• pixelMode: true (spec-level): camera offsets round to whole pixels, image smoothing is off
  for the frame, and bars, hbars, rings, emitter, particles and image draw on whole
  pixels, so on a solid background every pixel they draw is exactly a palette colour (bars at a
  248.025 px pitch: 2 colours, previously 26). Emitter particles show while their fade is at
  least one half. Constitution 6.2.0: "The format" names pixelMode.
• tone2 on bars (alternate, peak) and rings (alternate): the second tone fg2
  (roles.fg2 in creative mode, else mid grey).
• versus-bars: two opposed health bars whose health and damage tail come from the frame's
  coords, with whole-pixel stepped ends. hud-score: arcade read-outs (1UP, HI-SCORE,
  CREDIT, or a versus timer and names) from the frame's labels.
• ticker: the frame's labels as a scrolling news band; the centre item turns accent on loud
  frames.
• Style profiles in the user guide: CPS II versus stage (384 × 224) and arcade tate
  (224 × 288). The CRT finish stays Motion Studio's (#90).
• Showcase: print-exact, cps2-versus, tate-shooter and news-ticker; gallery demos for
  the three new primitives.
• dither renders about five times faster with byte-identical frames, so its default layer
  stays inside the 50 ms budget on CI runners.