Name every icon by the pixel grid it is drawn for

Groundwork for redrawing the icons on their pixel grids. A name is now
<icon><px> (server14, server16, server24) and must match the size token
where it renders: 14 at --icon-size-sm, 16 at -md, 24 at -xl.
tdesignLoading is the one exception, since it spins. Every name not yet
redrawn aliases its TDesign glyph, so nothing changes on screen except
the manager-open overlay icon, which moves from lg to xl ("a status
mark on a card").

- pixel-icons.ts holds the redrawn glyphs, so far add14 (the + from
  3f7145d, renamed from pixelAdd).
- TS code that picks icons takes Icon14 / Icon16 (menu items, file
  glyphs, the copy arrow, toasts, transfer states), so build:ui
  rejects a wrong name.
- icons.spec.ts checks every <ng-icon> in the skins: it has a size
  token, and each literal name, both sides of a [name] ternary
  included, is registered and drawn for that token's grid.
- TDesign's file1 is now fileText, since file1 plus a suffix would
  read file114.

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

docs/gotchas.md

@@ -86,7 +86,7 @@ touching the adjacent code.
   small size.** At 12 or 14px the centre is a pixel boundary, so a ~1px bar
   covers two pixels at half ink. A 1px stroke alone doesn't help, because the
   bar stays centred on the boundary. This is geometry, not Electrobun:
-  headless Chrome renders the same. So the + is `pixelAdd` (`icons.ts`),
+  headless Chrome renders the same. So the + is `add14` (`pixel-icons.ts`),
   redrawn on the 14px grid with 1px bars at 7.5, which fill whole pixels at 1x
   and at 2x. It's tuned for `--icon-size-sm` only. Arrow shafts (↑ →) have
   the same issue if it ever shows.