Text: text layers are always rasterised at their on-screen scale (#390)

Text is vector in After Effects and stays sharp at any Scale. Here a
text layer was drawn at its font size and the bitmap resampled by Scale
unless Continuously Rasterize was on, so text grown with Scale went soft.
This reworks #200 (reverted in 29c4d3a for kinetic_typography).

Why kinetic_typography failed: its time remap key at 1.9 s sits on
frame 23 (1.917 s), so main-comp 0.3 s shows the precomp at 1.6026 s,
but the test compared it with the precomp rendered at 1.6 s. The moving,
motion-blurred title already differed by 0.89 of the 1.0 mean-difference
budget on main (0.987 in all); with continuous rasterisation the "Sub"
line, whose expression scale is 84.00 % at 1.6 s and 84.105 % at
1.6026 s, falls on either side of the 2^-1/4 quarter-octave step and was
drawn at 0.84 at one time and at 1.0 at the other, pushing the total to
1.075.

Fix: raster_scale treats text layers as always continuously rasterised
(shape layers and vector footage still follow the switch), and rounds
the quarter-octave step up past rounding noise only: an unscaled layer
at a fractional position measured its scale as 1 + 1e-15 and was
rasterised at 2^1/4, softening unscaled text. The QA test now compares
the remapped precomp with the precomp at the time the remap really
shows (read back from the property): difference 0.63, all of it the
title's motion blur, the Sub line identical.

Tests: tests_collapse::text_scaled_up_stays_sharp_without_the_switch
(from #200: 10 px text at 800 % matches 80 px text),
tests_collapse::unscaled_text_rasterises_at_the_output_scale (fails
without the noise tolerance), automation qa kinetic_typography.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

docs/architecture.md

@@ -355,8 +355,9 @@ hierarchical block-matching optical flow and a bidirectional warp (Pixel Motion,
 its nested layers straight into the parent with concatenated transforms (one resample), so
 nested blend modes and adjustment layers act on the parent's layers; nested 3D layers use the
 parent's camera and lights and, when the precomp layer is 3D, are depth-sorted with the parent's
-3D run. Masks, effects or styles force a flattened render. On text and shape layers the switch is
-Continuously Rasterize: the source is rasterised at its on-screen scale. Quality: Draft samples
+3D run. Masks, effects or styles force a flattened render. Text layers are always rasterised at
+their on-screen scale, as text is vector in After Effects; on shape layers and vector footage the
+switch is Continuously Rasterize and does the same. Quality: Draft samples
 nearest-neighbour, Wireframe draws the layer bounds. Slip edit (`layer.slip`, Alt+PageUp/Down,
 dragging the source bar in the timeline) moves the source under fixed in/out points.
 

docs/parity.md

@@ -412,6 +412,9 @@ Fixes from measured reports:
   Stroke) blend onto the layer's colour inside its alpha, so an anti-aliased edge no longer shows
   a rim of the layer's own fill (#416). Not yet: Inner Bevel still shades an anti-aliased edge
   over the layer's own colour.
+- Text layers are always rasterised at their on-screen scale, sharp at any Scale as in After
+  Effects, and an unscaled layer at a fractional position is no longer rasterised a quarter octave
+  too large (#390).
 
 ## Update: plug-ins and extensions as in After Effects; ease presets become a ScriptUI panel