chore(tui): /clean pass — inline one-off locals, tighten ConfirmPrompt

- providers.ts: drop the `dup` intermediate, fold the ternary inline
- paths.ts (fmtCwdBranch): inline `b` into the `tag` template
- prompts.tsx (ConfirmPrompt): hoist a single `lower = ch.toLowerCase()`,
  collapse the three early-return branches into two, drop the
  redundant bounds checks on arrow-key handlers (setSel is idempotent
  at 0/1), inline the `confirmLabel`/`cancelLabel` defaults at the
  use site
- modelPicker.tsx / config/env.ts / providers.test.ts: auto-formatter
  reflows picked up by `npm run fix`
- useInputHandlers.ts: drop the stray blank line that was tripping
  perfectionist/sort-imports (pre-existing lint error)

ui-tui/src/domain/providers.ts

@@ -5,13 +5,7 @@ export const providerDisplayNames = (providers: readonly { name: string; slug: s
     counts.set(p.name, (counts.get(p.name) ?? 0) + 1)
   }
 
-  return providers.map(p => {
-    const dup = (counts.get(p.name) ?? 0) > 1
-
-    if (!dup || !p.slug || p.slug === p.name) {
-      return p.name
-    }
-
-    return `${p.name} (${p.slug})`
-  })
+  return providers.map(p =>
+    (counts.get(p.name) ?? 0) > 1 && p.slug && p.slug !== p.name ? `${p.name} (${p.slug})` : p.name
+  )
 }