fix(uix): focus ring on surfaces — migrate 5 box-shadow rings to outline

The box-shadow token --focus-ring hardcodes var(--color-surface-default) as its
gap-fill (render-css.ts:184), so a control focused inside a raised/overlay/filled
plane showed a mismatched halo; box-shadow rings are also clipped by overflow:hidden
and die under forced-colors. Migrate the last 5 box-shadow consumers to the canonical
outline pattern already used by button/card/~40 components:

  outline: var(--focus-ring-width) solid var(--focus-ring-color)
  outline-offset: var(--focus-ring-offset)   (or 0, flush, for input + scrollbar)

- command-input (offset 0, keeps border-color shift) - collapsible-trigger - toggle -
  splitter-resize-trigger (offset var) - scroll-area-scrollbar (offset 0)

Outline follows border-radius on every evergreen browser, isn't clipped by overflow,
and the forced-colors fallback already maps outline. The gap-color mismatch disappears
-- no --focus-ring-surface token needed.

NOTE: the box-shadow token --focus-ring now has zero CSS consumers (only THEMING.md +
a palabras doc reference it). Left in place -- it's a public foundation token; removing
it is a separate API decision (bundle with the --size-* orphan cleanup).

Verified: grep 0 box-shadow focus rings in component CSS; eidos suite 15/239 unchanged;
served rule confirmed in browser ([data-toggle]:focus-visible -> outline). Visual look
on keyboard focus worth a live Tab-through (CDP screenshot hung all session).

src/uix/eidos/components/collapsible/collapsible.css

@@ -57,8 +57,8 @@
 }
 
 [data-collapsible-trigger]:focus-visible {
-	outline: none;
-	box-shadow: var(--focus-ring);
+	outline: var(--focus-ring-width) solid var(--focus-ring-color);
+	outline-offset: var(--focus-ring-offset);
 }
 
 [data-collapsible-trigger][data-disabled] {

src/uix/eidos/components/command/command.css

@@ -139,7 +139,8 @@
 
 [data-command-input]:focus-visible {
 	border-color: var(--color-primary-border);
-	box-shadow: var(--focus-ring);
+	outline: var(--focus-ring-width) solid var(--focus-ring-color);
+	outline-offset: 0;
 }
 
 [data-command-input]::placeholder {

src/uix/eidos/components/scroll-area/scroll-area.css

@@ -110,8 +110,8 @@
 }
 
 [data-scroll-area-scrollbar]:focus-visible {
-	outline: none;
-	box-shadow: var(--focus-ring);
+	outline: var(--focus-ring-width) solid var(--focus-ring-color);
+	outline-offset: 0;
 }
 
 [data-scroll-area-thumb] {

src/uix/eidos/components/splitter/splitter.css

@@ -70,8 +70,8 @@
 }
 
 [data-splitter-resize-trigger]:focus-visible {
-	outline: none;
-	box-shadow: var(--focus-ring);
+	outline: var(--focus-ring-width) solid var(--focus-ring-color);
+	outline-offset: var(--focus-ring-offset);
 }
 
 [data-splitter-resize-trigger][data-state='dragging'],

src/uix/eidos/components/toggle/toggle.css

@@ -152,8 +152,8 @@
 }
 
 [data-toggle]:focus-visible {
-	outline: none;
-	box-shadow: var(--focus-ring);
+	outline: var(--focus-ring-width) solid var(--focus-ring-color);
+	outline-offset: var(--focus-ring-offset);
 }
 
 [data-toggle][data-block] {