feat(turbo): turbo gen feature generator (Phase 1, single-entity)

Adds `pnpm turbo gen feature` to scaffold a Lazar-conformant feature
package matching the navigation reference shape: entity + Zod schema,
single use case (`get<Entity>`), controller, mock + Payload-stub real
repository (with span + capture), DI module/container/symbols, and tRPC
router with full BAD_REQUEST/NOT_FOUND error mapping. The generated
`bind-production.ts` and `bind-dev-seed.ts` compose the post-R44
`withSpan(tracer, opts, withCapture(logger, tags, factory(deps)))`
sandwich at bind time.

Verified by generating a sample `packages/example/` feature and running
`pnpm --filter @repo/example lint typecheck test` — all three pass
(9 test files, 25 tests). Cleaned up after verification so no example
package is committed.

Phase-1 limitations (documented in `docs/guides/scaffolding-a-feature.md`
and printed by the generator on success): no Payload CMS templates, no
React Query helpers, faker-driven factories left as stubs, single
entity / single use case, and aggregator wiring (core-api/root,
apps/web-next bindAll) is left as a manual checklist.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

turbo/generators/templates/feature/src/application/use-cases/get-entity.use-case.test.ts.hbs

@@ -0,0 +1,31 @@
+import { describe, expect, it } from "vitest";
+import { ZodError } from "zod";
+import { get{{pascalCase entity}}UseCase } from "@/application/use-cases/get-{{kebabCase entity}}.use-case";
+import { Mock{{pascalCase entity}}Repository } from "@/infrastructure/repositories/{{kebabCase entity}}.repository.mock";
+import { {{pascalCase entity}}NotFoundError } from "@/entities/errors/{{kebabCase entity}}";
+
+describe("get{{pascalCase entity}}UseCase", () => {
+  it("returns the seeded {{camelCase entity}} by id", async () => {
+    const repo = new Mock{{pascalCase entity}}Repository();
+    const useCase = get{{pascalCase entity}}UseCase(repo);
+    const result = await useCase({ id: "seed-1" });
+    expect(result.id).toBe("seed-1");
+    expect(result.name).toBeTypeOf("string");
+  });
+
+  it("throws {{pascalCase entity}}NotFoundError when repository returns null", async () => {
+    const repo = new Mock{{pascalCase entity}}Repository(new Map());
+    const useCase = get{{pascalCase entity}}UseCase(repo);
+    await expect(useCase({ id: "missing" })).rejects.toBeInstanceOf(
+      {{pascalCase entity}}NotFoundError,
+    );
+  });
+
+  it("throws ZodError when repository returns malformed data", async () => {
+    const malformedRepo = {
+      get{{pascalCase entity}}: async () => ({ id: "", name: "x" }) as never,
+    };
+    const useCase = get{{pascalCase entity}}UseCase(malformedRepo);
+    await expect(useCase({ id: "anything" })).rejects.toBeInstanceOf(ZodError);
+  });
+});

turbo/generators/templates/feature/src/application/use-cases/get-entity.use-case.ts.hbs

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+import { z } from "zod";
+
+import { {{pascalCase entity}}NotFoundError } from "../../entities/errors/{{kebabCase entity}}";
+import { {{camelCase entity}}Schema } from "../../entities/models/{{kebabCase entity}}";
+import type { I{{pascalCase entity}}Repository } from "../repositories/{{kebabCase entity}}.repository.interface";
+
+// ── Input ────────────────────────────────────────────────────────────────
+export const get{{pascalCase entity}}InputSchema = z
+  .object({
+    id: z.string().min(1),
+  })
+  .strict();
+export type Get{{pascalCase entity}}Input = z.infer<typeof get{{pascalCase entity}}InputSchema>;
+
+// ── Output ───────────────────────────────────────────────────────────────
+export const get{{pascalCase entity}}OutputSchema = {{camelCase entity}}Schema;
+export type Get{{pascalCase entity}}Output = z.infer<typeof get{{pascalCase entity}}OutputSchema>;
+
+// ── Use case ─────────────────────────────────────────────────────────────
+export type IGet{{pascalCase entity}}UseCase = ReturnType<typeof get{{pascalCase entity}}UseCase>;
+
+export const get{{pascalCase entity}}UseCase =
+  ({{camelCase entity}}Repository: I{{pascalCase entity}}Repository) =>
+  async (input: Get{{pascalCase entity}}Input): Promise<Get{{pascalCase entity}}Output> => {
+    const result = await {{camelCase entity}}Repository.get{{pascalCase entity}}(input.id);
+    if (!result) {
+      throw new {{pascalCase entity}}NotFoundError(`{{pascalCase entity}} not found: ${input.id}`);
+    }
+    return get{{pascalCase entity}}OutputSchema.parse(result);
+  };