feat: add dependency direction enforcement (v0.4.0)

Implement dependency direction detection to enforce Clean Architecture rules:
- Domain layer can only import from Domain and Shared
- Application layer can only import from Domain, Application, and Shared
- Infrastructure layer can import from all layers
- Shared layer can be imported by all layers

Added:
- IDependencyDirectionDetector interface in domain layer
- DependencyViolation value object with detailed suggestions and examples
- DependencyDirectionDetector implementation in infrastructure
- Integration with AnalyzeProject use case
- New DEPENDENCY_DIRECTION rule in constants
- 43 comprehensive tests covering all scenarios (100% passing)
- Good and bad examples in examples directory

Improvements:
- Optimized extractLayerFromImport method to reduce complexity
- Fixed indentation in DependencyGraph.ts
- Updated getExampleFix to avoid false positives in old detector

Test Results:
- All 261 tests passing
- Build successful
- Self-check: 0 architecture violations in src code

packages/guardian/examples/bad-architecture/dependency-direction/BadApplicationLayer.ts

@@ -0,0 +1,117 @@
+/**
+ * ❌ BAD: Application layer with incorrect dependencies
+ *
+ * Application importing from Infrastructure layer
+ * This violates Clean Architecture dependency rules!
+ */
+
+import { User } from "../../good-architecture/domain/entities/User"
+import { Email } from "../../good-architecture/domain/value-objects/Email"
+import { UserId } from "../../good-architecture/domain/value-objects/UserId"
+
+/**
+ * ❌ VIOLATION: Application importing from Infrastructure layer
+ */
+import { PrismaClient } from "@prisma/client"
+
+export class CreateUser {
+    /**
+     * ❌ VIOLATION: Application use case depending on concrete infrastructure (Prisma)
+     */
+    constructor(private prisma: PrismaClient) {}
+
+    async execute(email: string): Promise<User> {
+        const userId = UserId.generate()
+        const emailVO = Email.create(email).value
+
+        /**
+         * ❌ VIOLATION: Application logic directly accessing database
+         */
+        await this.prisma.user.create({
+            data: {
+                id: userId.getValue(),
+                email: emailVO.getValue(),
+            },
+        })
+
+        return new User(userId, emailVO)
+    }
+}
+
+/**
+ * ❌ VIOLATION: Application importing concrete email service from infrastructure
+ */
+import { SmtpEmailService } from "../../good-architecture/infrastructure/adapters/SmtpEmailService"
+
+export class SendWelcomeEmail {
+    /**
+     * ❌ VIOLATION: Application depending on concrete infrastructure implementation
+     * Should depend on IEmailService interface instead
+     */
+    constructor(
+        private prisma: PrismaClient,
+        private emailService: SmtpEmailService,
+    ) {}
+
+    async execute(userId: string): Promise<void> {
+        const user = await this.prisma.user.findUnique({
+            where: { id: userId },
+        })
+
+        if (!user) {
+            throw new Error("User not found")
+        }
+
+        await this.emailService.sendWelcomeEmail(user.email)
+    }
+}
+
+/**
+ * ❌ VIOLATION: Application importing from infrastructure controller
+ */
+import { UserController } from "../../good-architecture/infrastructure/controllers/UserController"
+
+export class ValidateUser {
+    /**
+     * ❌ VIOLATION: Application use case depending on infrastructure controller
+     * The dependency direction is completely wrong!
+     */
+    constructor(private userController: UserController) {}
+
+    async execute(userId: string): Promise<boolean> {
+        return true
+    }
+}
+
+/**
+ * ❌ VIOLATION: Application importing HTTP framework
+ */
+import express from "express"
+
+export class ProcessUserRequest {
+    /**
+     * ❌ VIOLATION: Application layer knows about HTTP/Express
+     * HTTP concerns should be in infrastructure layer
+     */
+    async execute(req: express.Request): Promise<void> {
+        const email = req.body.email
+        console.log(`Processing user: ${email}`)
+    }
+}
+
+/**
+ * ❌ VIOLATION: Application importing infrastructure repository implementation
+ */
+import { InMemoryUserRepository } from "../../good-architecture/infrastructure/repositories/InMemoryUserRepository"
+
+export class GetUser {
+    /**
+     * ❌ VIOLATION: Application depending on concrete repository implementation
+     * Should depend on IUserRepository interface from domain
+     */
+    constructor(private userRepo: InMemoryUserRepository) {}
+
+    async execute(userId: string): Promise<User | null> {
+        return await this.userRepo.findById(UserId.from(userId))
+    }
+}

packages/guardian/examples/bad-architecture/dependency-direction/BadDomainLayer.ts

@@ -0,0 +1,90 @@
+/**
+ * ❌ BAD: Domain layer with incorrect dependencies
+ *
+ * Domain importing from Application and Infrastructure layers
+ * This violates Clean Architecture dependency rules!
+ */
+
+import { Email } from "../../good-architecture/domain/value-objects/Email"
+import { UserId } from "../../good-architecture/domain/value-objects/UserId"
+
+/**
+ * ❌ VIOLATION: Domain importing from Application layer
+ */
+import { UserResponseDto } from "../../good-architecture/application/dtos/UserResponseDto"
+
+export class User {
+    private readonly id: UserId
+    private email: Email
+
+    constructor(id: UserId, email: Email) {
+        this.id = id
+        this.email = email
+    }
+
+    /**
+     * ❌ VIOLATION: Domain entity returning DTO from application layer
+     */
+    toDto(): UserResponseDto {
+        return {
+            id: this.id.getValue(),
+            email: this.email.getValue(),
+            createdAt: new Date().toISOString(),
+        }
+    }
+}
+
+/**
+ * ❌ VIOLATION: Domain importing from Infrastructure layer
+ */
+import { PrismaClient } from "@prisma/client"
+
+export class UserService {
+    /**
+     * ❌ VIOLATION: Domain service depending on concrete infrastructure implementation
+     */
+    constructor(private prisma: PrismaClient) {}
+
+    async createUser(email: string): Promise<User> {
+        const userId = UserId.generate()
+        const emailVO = Email.create(email).value
+
+        /**
+         * ❌ VIOLATION: Domain logic directly accessing database
+         */
+        await this.prisma.user.create({
+            data: {
+                id: userId.getValue(),
+                email: emailVO.getValue(),
+            },
+        })
+
+        return new User(userId, emailVO)
+    }
+}
+
+/**
+ * ❌ VIOLATION: Domain importing email service from infrastructure
+ */
+import { SmtpEmailService } from "../../good-architecture/infrastructure/adapters/SmtpEmailService"
+
+export class UserRegistration {
+    /**
+     * ❌ VIOLATION: Domain depending on infrastructure email service
+     */
+    constructor(
+        private userService: UserService,
+        private emailService: SmtpEmailService,
+    ) {}
+
+    async register(email: string): Promise<User> {
+        const user = await this.userService.createUser(email)
+
+        /**
+         * ❌ VIOLATION: Domain calling infrastructure service directly
+         */
+        await this.emailService.sendWelcomeEmail(email)
+
+        return user
+    }
+}