gui: a renderer redraws its pieces and never the widget, and the explanation sheet says when it changes (#106)

* gui: a renderer redraws its pieces and never the widget, and the explanation sheet says when it changes

The explanation behind the (i) button did not open on the first hover of a
fresh window, and did after hovering a tab word first. Measured with a copy
of the window whose driver logged every refresh: canvas.Refresh(r.button)
asked for the Button embedded inside DetailButton, while the tree and the
driver's object-to-canvas cache hold the DetailButton - a different
interface value, so no canvas was found, nothing was marked dirty and the
box put on the sheet was never painted until something else repainted for
its own reason. The test driver cannot see this: it answers CanvasForObject
for any object and its canvas ignores Refresh.

- parts: redraw(pieces...) - every renderer names the pieces it draws,
  seven renderers unified, no canvas.Refresh left in parts or window
- parts: Tips.open and close refresh the sheet, which also fixes the
  keyboard path - Space on the focused button added a box nothing painted
  and removed one that stayed drawn
- guard: canvastold_test.go reads both rules from the source, since nothing
  behavioural can; detailpopup_test.go hovers through the canvas on the
  visible screen and refuses a button drawn nowhere
- screens: generate-hovered and generate-refused-setting regenerated - both
  had captured a stale icon raster, the painter behind the stored pictures
  keeping an image until the image itself is refreshed

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

* guard: a renderer names every piece it changes, and a box is refreshed after its last change

Two things an outside review of the pull request pointed at, both about
the guard and neither about the window.

The renderer rule counted the arguments of redraw and asked nothing of
them, so a face setting four pieces and naming three passed. It now reads
every field set on a piece and every piece shown, through the renderer's
own methods, and requires each to be named - Show on a canvas primitive
or a container sets Hidden and stops in the pinned toolkit, where Hide,
Move and Resize repaint by themselves. Measured on the seven renderers:
21 pieces changed, all named, and dropping any one of them turns it red.

The box rule accepted a refresh anywhere in the method, so a refresh
standing before the change counted. It now takes the last change and the
last refresh and requires that order. What it still cannot see is written
at the top of the file.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

* changelog: the explanation opens on the first hover and from the keyboard

The fix in this pull request is one a person sees, and every other
change under Unreleased that a person sees has its entry - an outside
review pointed at the missing one.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 5 <noreply@anthropic.com>

Author: donislawdev

CHANGELOG.md

@@ -134,6 +134,14 @@ because it turns other people's test suites red.
 
 ### Fixed
 
+- **The explanation beside a field opens on the first hover, and opens and
+  closes from the keyboard.** Pointing at the information mark in a fresh
+  window showed nothing until something else on the screen happened to
+  repaint, and Space on the mark with the keyboard drew nothing at all. The
+  window's controls now tell the canvas about each piece they change, and the
+  sheet the explanation is drawn on says so when a box is put on it or taken
+  off.
+
 - **A refused preset no longer carries the note of the preset before it.** A
   limit of 512 B was refused with "no limit was given" under it - a note left
   over from the last expansion that worked.