feat(generators): core-ui-component generator + action helpers + tests

Adds the setGenerator("core-ui-component") block, coreUiComponentActions
helper (2 guards + 4 add + 1 modify + 1 print = 8 actions), and
printCoreUiComponentNextSteps to config.ts; covers all three paths with
3 new unit tests in config.test.ts (registration shape, action shape per
tier, PascalCase validator). Generator test count: 17 → 20.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

turbo/generators/config.ts

@@ -736,6 +736,49 @@ import noRealtimeHandlerReexport from "./rules/no-realtime-handler-reexport.js";
       return jobActions(a);
     },
   });
+
+  /**
+   * Turbo generator: `core-ui-component`
+   *
+   * Scaffolds a core-ui atomic-design component (atom / molecule / organism)
+   * using the established 4-file pattern: `<name>.tsx`, `<name>.stories.tsx`,
+   * `<name>.test.tsx`, `index.ts`. Splices the new export into the matching
+   * tier barrel via the `// <gen:<tier>s>` anchor.
+   *
+   * Refuses to run unless `packages/core-ui/` exists (see
+   * `pnpm turbo gen core-package ui`).
+   */
+  plop.setGenerator("core-ui-component", {
+    description:
+      "Scaffold a core-ui atomic-design component (atom / molecule / organism)",
+    prompts: [
+      {
+        type: "list",
+        name: "tier",
+        message: "Tier:",
+        choices: ["atom", "molecule", "organism"],
+      },
+      {
+        type: "input",
+        name: "name",
+        message: "Component name (PascalCase, e.g. Spinner):",
+        validate: (input: string) => {
+          if (!input) return "Required";
+          if (!/^[A-Z][A-Za-z0-9]*$/.test(input)) {
+            return "Must be PascalCase (e.g. Spinner, IconButton)";
+          }
+          return true;
+        },
+      },
+    ],
+    actions: (answers) => {
+      const a = answers as {
+        tier: "atom" | "molecule" | "organism";
+        name: string;
+      };
+      return coreUiComponentActions(a);
+    },
+  });
 }
 
 function jobActions(a: {
@@ -1281,6 +1324,106 @@ function printRealtimeNextSteps(): string {
   ].join("\n");
 }
 
+function coreUiComponentActions(a: {
+  tier: "atom" | "molecule" | "organism";
+  name: string;
+}): PlopTypes.ActionType[] {
+  const tierPlural = `${a.tier}s` as const;
+  const tierTitle = tierPlural[0]!.toUpperCase() + tierPlural.slice(1);
+  const tierBarrel = `packages/core-ui/src/${tierPlural}/index.ts`;
+  const componentDir = `packages/core-ui/src/${tierPlural}/{{kebabCase name}}`;
+
+  return [
+    // 1. Guard: core-ui must be scaffolded
+    () => {
+      const pkgRoot = join(process.cwd(), "packages", "core-ui");
+      if (!existsSync(pkgRoot)) {
+        throw new Error(
+          `packages/core-ui/ does not exist. Run \`pnpm turbo gen core-package ui\` first.`,
+        );
+      }
+      return "Guard passed — packages/core-ui exists.";
+    },
+
+    // 2. Guard: tier barrel must have its anchor
+    () => {
+      assertAnchors(process.cwd(), tierBarrel, [`// <gen:${tierPlural}>`]);
+      return `Anchor // <gen:${tierPlural}> present in ${tierBarrel}.`;
+    },
+
+    // 3. Emit the 4 component files
+    {
+      type: "add",
+      path: `${componentDir}/{{kebabCase name}}.tsx`,
+      templateFile: "templates/core-ui-component/component.tsx.hbs",
+      data: { name: a.name },
+    },
+    {
+      type: "add",
+      path: `${componentDir}/{{kebabCase name}}.stories.tsx`,
+      templateFile: "templates/core-ui-component/component.stories.tsx.hbs",
+      data: { name: a.name, tierTitle },
+    },
+    {
+      type: "add",
+      path: `${componentDir}/{{kebabCase name}}.test.tsx`,
+      templateFile: "templates/core-ui-component/component.test.tsx.hbs",
+      data: { name: a.name },
+    },
+    {
+      type: "add",
+      path: `${componentDir}/index.ts`,
+      templateFile: "templates/core-ui-component/index.ts.hbs",
+      data: { name: a.name },
+    },
+
+    // 4. Splice export into tier barrel.
+    //    The `template` string is itself Handlebars-rendered by plop, so
+    //    {{pascalCase name}} and {{kebabCase name}} are resolved at apply-
+    //    time. This matches the pattern used by the `realtime` and `event`
+    //    generators (no kebabCase JS helper exists in config.ts).
+    {
+      type: "modify",
+      path: tierBarrel,
+      pattern: new RegExp(`// <gen:${tierPlural}>`),
+      template: `// <gen:${tierPlural}>\nexport { {{pascalCase name}}, type {{pascalCase name}}Props } from "./{{kebabCase name}}/index";`,
+    },
+
+    // 5. Print next-steps
+    () => printCoreUiComponentNextSteps(a),
+  ];
+}
+
+function printCoreUiComponentNextSteps(a: {
+  tier: "atom" | "molecule" | "organism";
+  name: string;
+}): string {
+  const tierPlural = `${a.tier}s`;
+  const kebab = a.name
+    .replace(/([a-z0-9])([A-Z])/g, "$1-$2")
+    .replace(/([A-Z]+)([A-Z][a-z])/g, "$1-$2")
+    .toLowerCase();
+  const pascal = a.name;
+  return [
+    "─────────────────────────────────────────────────────────────",
+    `${pascal} scaffolded into packages/core-ui/src/${tierPlural}/${kebab}/.`,
+    "",
+    "Next steps (manual):",
+    `  1. Implement the component body in ${kebab}.tsx (currently a div`,
+    `     passthrough — change the element/type to fit, add variants/sizes`,
+    `     if needed; see button.tsx for the canonical rich pattern).`,
+    `  2. Flesh out the Default story in ${kebab}.stories.tsx; add variant`,
+    `     stories if your component takes a variant prop.`,
+    `  3. Tighten the tests in ${kebab}.test.tsx beyond the smoke-test`,
+    `     baseline.`,
+    "",
+    "Verify:",
+    "  pnpm --filter @repo/core-ui lint typecheck test",
+    "  pnpm dev --filter @repo/storybook   # view in Storybook",
+    "─────────────────────────────────────────────────────────────",
+  ].join("\n");
+}
+
 // Local helpers used inside the printNextSteps action — Plop's helpers aren't
 // available outside template strings, so we replicate the bits we need.
 function cap(input: string): string {