feat(conformance): implement ReadOnly brand and reader generator

- Add ReadOnly<F> phantom brand to core-shared/conformance (compile-time
  enforcement that readers only wrap non-mutating use cases)
- Add isReadOnly runtime predicate for boot-time assertReaderPurity
- Scaffold pnpm turbo gen reader: creates integrations/readers/ with
  interface, implementation, test, barrel, and adds ./reader export
  subpath to package.json

turbo/generators/templates/reader/index.ts.hbs

@@ -0,0 +1,3 @@
+// packages/{{kebabCase feature}}/src/integrations/readers/index.ts
+// Public surface: type-only export. Implementation is internal.
+export type { I{{pascalCase feature}}Reader } from "./{{kebabCase feature}}.reader.interface";

turbo/generators/templates/reader/reader.interface.ts.hbs

@@ -0,0 +1,14 @@
+// packages/{{kebabCase feature}}/src/integrations/readers/{{kebabCase feature}}.reader.interface.ts
+
+/**
+ * Cross-feature read-only query contract for the {{kebabCase feature}} vertical.
+ * Consumers import this type from `@repo/{{kebabCase feature}}/reader`.
+ * Implementation is private — constructed by the feature's binder.
+ *
+ * Rules: Q0 (cross-feature domain queries only), Q1 (interface public,
+ * impl private), Q2 (read-only — wraps only mutates:false use cases).
+ */
+export interface I{{pascalCase feature}}Reader {
+  // Add methods as consumers need them. Each method must delegate to a
+  // use case declared mutates: false in feature.manifest.ts.
+}

turbo/generators/templates/reader/reader.test.ts.hbs

@@ -0,0 +1,10 @@
+// packages/{{kebabCase feature}}/src/integrations/readers/{{kebabCase feature}}.reader.test.ts
+import { describe, it, expect } from "vitest";
+import { {{pascalCase feature}}Reader } from "@/integrations/readers/{{kebabCase feature}}.reader";
+
+describe("{{pascalCase feature}}Reader", () => {
+  it("can be constructed", () => {
+    const reader = new {{pascalCase feature}}Reader();
+    expect(reader).toBeDefined();
+  });
+});

turbo/generators/templates/reader/reader.ts.hbs

@@ -0,0 +1,25 @@
+// packages/{{kebabCase feature}}/src/integrations/readers/{{kebabCase feature}}.reader.ts
+
+import type { I{{pascalCase feature}}Reader } from "./{{kebabCase feature}}.reader.interface";
+
+/**
+ * Internal implementation of I{{pascalCase feature}}Reader.
+ * Wraps existing use cases — does not add domain logic.
+ * Constructed by bind-production / bind-dev-seed; never exported.
+ *
+ * All injected use cases MUST be ReadOnly-branded (mutates: false).
+ */
+export class {{pascalCase feature}}Reader implements I{{pascalCase feature}}Reader {
+  // Inject ReadOnly-branded use cases via constructor:
+  //
+  // constructor(
+  //   private getUser: ReadOnly<IGetUserUseCase>,
+  // ) {}
+  //
+  // Then delegate:
+  //
+  // async exists(userId: string): Promise<boolean> {
+  //   const user = await this.getUser({ id: userId });
+  //   return user !== null;
+  // }
+}