fix(ui): draw one focus ring, not two

src/index.css already declared "one visible, consistent focus treatment",
but shadcn's primitives ship a `focus-visible:ring-[3px]` of their own, so
every button and input actually drew two: a soft translucent halo hugging
the border, then a hard 2px outline 2px further out.

The global rule is the one that stays, because it also covers the links and
bare table buttons that never go through a primitive. The rings come out of
button.tsx and input.tsx instead.

Its `border-radius: 2px` goes too. That was squaring the corners of every
control with no radius utility of its own — the rule-history triggers in
Settings measured `rad=0`, so a focused one drew a sharp rectangle. The
outline now follows each element's own radius.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

src/index.css

@@ -173,11 +173,18 @@
   }
 
   /* One visible, consistent focus treatment. Keyboard users get a ring on the
-     accent colour, which clears 3:1 on every surface in both themes. */
+     accent colour, which clears 3:1 on every surface in both themes.
+     Deliberately the ONLY focus indicator: shadcn's primitives ship a second,
+     softer `ring` box-shadow of their own, and the two together read as a halo
+     inside a line. Those are stripped in button.tsx and input.tsx instead of
+     dropping this, because this one rule covers links, table buttons and
+     anything else that never goes through a primitive.
+     It sets no border-radius on purpose — an earlier version pinned 2px here,
+     which squared the corners of every control that had no radius utility of
+     its own. The outline follows each element's own radius. */
   :focus-visible {
     outline: 2px solid var(--budget-accent);
     outline-offset: 2px;
-    border-radius: 2px;
   }
 }