Describe per-frame previews of inspector rows and tabs (#274)

- Architecture: inspector rows and colour stops preview once per
  frame, with the measured numbers. The Pixel art tab's side panel
  and the Curve tab's fields follow the same rule.
- Development: 1616 editor checks.

Architecture.md

@@ -339,8 +339,15 @@ graph canvases (nodes, groups, comments) use it. Measured with 120 extra objects
 120 pointer moves 8 ms apart: 26, 34 and 29 ms per move before, 18, 18 and 17 after (the probe's
 own pause and round trip are in every number). The Texture tab had been paying twice: Pixi repeats the
 last pointer move a few milliseconds later to update hover, with the same native event, and
-each one ran a full preview. Inspector scrubbing and the gradient bar's colour stops still preview
-on every move.
+each one ran a full preview.
+
+The inspector's rows and the gradient bar's colour stops go the same way (#274). `previewingHandlers`
+asks for the frame on every input, whether scrubbed, typed or picked, and cancels it before the
+command; the bar's `preview` handler in `shapeSection.ts` does the same. Both had been paying twice
+as well: the same probe counted 236 project events for 120 moves of a scrub and 238 for a colour
+stop, at 47 ms per move. Now it is 51 to 61 events and 22 ms per move. The Pixel art tab's side
+panel (the colour of a palette swatch, the opacity of a layer) and the Curve tab's `t` and `v`
+fields follow the same rule; those were changed without a measurement of their own.
 
 The Texture tab draws its frames in two layers (#220). `sheet` holds every frame but the selected
 one with its outlines, `overlay` the selected frame, its handles and a frame being spanned. Both

Development.md

@@ -18,7 +18,7 @@ php tests/php/accounts.test.php                               # the API's accoun
                                                               #   has and the web server's container has not (SKIP there)
 php tests/php/snapshots.test.php                              # the snapshot store (#231), the same way
 php tests/php/releases.test.php                               # the release store (#266), the same way
-node tools/seed-e2e.mjs && node tools/e2e.mjs                 # 1615 editor checks, screenshots in /tmp/gm-e2e-*.png
+node tools/seed-e2e.mjs && node tools/e2e.mjs                 # 1616 editor checks, screenshots in /tmp/gm-e2e-*.png
 GM_STEPS=20 node tools/e2e.mjs                                # or 1-12, or 6,20 — a subset while working on one step
 ./e2e.sh start [GM_STEPS]                                     # the same run detached, see below
 ./e2e.sh status                                               # live progress, or the last run's result