fix(tui): support single categorical theme hue

packages/theme/src/tui/syntax.ts

@@ -12,7 +12,7 @@ export function generateSyntax(theme: ResolvedThemeTokens, mode: Mode) {
     rule(["prompt"], theme.hue.accent[step]),
     rule(["extmark.file"], feedback.warning.default, { bold: true }),
     rule(["extmark.agent"], theme.categorical[0][step], { bold: true }),
-    rule(["extmark.skill"], theme.categorical[1][step], { bold: true }),
+    rule(["extmark.skill"], (theme.categorical[1] ?? theme.categorical[0])[step], { bold: true }),
     // V1 migration preserves its selected/inverse foreground in this action state.
     rule(["extmark.paste"], theme.text.action.primary.focused, {
       background: feedback.warning.default,

packages/tui/test/theme/v2/syntax.test.ts

@@ -0,0 +1,12 @@
+import { expect, test } from "bun:test"
+import { generateSyntax, resolveThemeDocument } from "@opencode-ai/theme/tui"
+import { SyntaxStyle } from "@opentui/core"
+import { parseTheme } from "../../../src/theme"
+
+test("generates syntax for a single categorical hue", () => {
+  const theme = resolveThemeDocument(parseTheme({ version: 2, light: { categorical: ["red"] } }), "light")
+  const syntax = generateSyntax(theme, "light")
+
+  expect(syntax).toBeInstanceOf(SyntaxStyle)
+  syntax.destroy()
+})