Add validation integration and macro-based route support

Introduces the ValidatedJson extractor for request body validation using the rustapi-validate crate, and integrates validation error conversion into ApiError. Adds Route and RouteHandler traits, route! macro, and mount_route for macro-based route registration. Updates dependencies and workspace configuration to include rustapi-validate. Removes AGENTS.md and Copilot instructions in favor of a unified .agent/INSTRUCTIONS.md.

Author: Tuntii

.agent/INSTRUCTIONS.md

@@ -0,0 +1,170 @@
+# RustAPI - Project Instructions
+
+> **Last Updated:** December 30, 2025  
+> **Status:** Phase 1 Complete ✅ | Phase 2 In Progress 🔄
+
+---
+
+## Project Overview
+
+**RustAPI** is a FastAPI-inspired web framework for Rust that prioritizes developer experience (DX) while maintaining Rust's performance and memory safety.
+
+### Core Philosophy
+- **5-line Hello World** - Minimal boilerplate
+- **Type-driven development** - Structs as schemas
+- **API surface is ours, engines can change** - All dependencies wrapped
+- **Batteries included but modular** - Easy start, escape hatches available
+
+---
+
+## Project Structure
+
+```
+RustAPI/
+├── Cargo.toml                    # Workspace root
+├── README.md                     # PRD + Manifesto (detailed)
+├── memories/
+│   ├── TASKLIST.md              # Phase-by-phase task list
+│   └── rustapi_memory_bank.md   # Technical reference + decisions
+├── crates/
+│   ├── rustapi-rs/              # Public facade (crates.io name)
+│   ├── rustapi-core/            # Router, extractors, responses, server
+│   ├── rustapi-macros/          # Proc-macros (#[rustapi::main], etc.)
+│   └── rustapi-validate/        # Validation system (validator wrapper)
+└── examples/
+    └── hello-world/             # Working example ✅
+```
+
+---
+
+## Phase Summary
+
+| Phase | Status | Description |
+|-------|--------|-------------|
+| Phase 1: MVP | ✅ Complete | Router, extractors, responses, basic server |
+| Phase 2: Validation + OpenAPI | 🔄 In Progress | Validation wrapper, OpenAPI docs, Swagger UI |
+| Phase 3: Batteries Included | ⏳ Planned | Middleware, JWT, CORS, rate limiting |
+| Phase 4: v1.0 | ⏳ Planned | Polish, tests, documentation, crates.io publish |
+
+---
+
+## Key Architecture Decisions
+
+1. **Crate name:** `rustapi-rs` (for crates.io)
+2. **validator crate:** Wrapper in v0.x, custom engine in v1.x
+3. **utoipa crate:** Wrapper only, never expose types
+4. **MSRV:** Rust 1.75+
+5. **Path params:** `{param}` format (converted to `:param` for matchit)
+
+---
+
+## Development Commands
+
+```powershell
+# Build entire workspace
+cargo build
+
+# Run hello-world example
+cargo run -p hello-world
+
+# Run tests
+cargo test --workspace
+
+# Test validation crate
+cargo test -p rustapi-validate
+
+# Test specific endpoint
+Invoke-RestMethod -Uri http://127.0.0.1:8080/
+Invoke-RestMethod -Uri http://127.0.0.1:8080/users/42
+```
+
+---
+
+## Current Implementation Status
+
+### ✅ Completed (Phase 1)
+- **Router:** Radix tree with matchit, path params, method routing
+- **Extractors:** `Json<T>`, `Path<T>`, `Query<T>`, `State<T>`, `Body`
+- **Responses:** `Json<T>`, `Created<T>`, `NoContent`, `Html<T>`, `Redirect`
+- **Errors:** `ApiError`, `Result<T>` type alias
+- **Server:** Hyper 1.x, graceful shutdown, tracing
+
+### 🔄 In Progress (Phase 2)
+- **Validation:** `rustapi-validate` crate exists with:
+  - `Validate` trait (wraps `validator::Validate`)
+  - `FieldError`, `ValidationError` types
+  - 422 JSON error format
+  - Tests passing
+- **Pending:**
+  - `ValidatedJson<T>` extractor
+  - Integration with `rustapi-core`
+  - `rustapi-openapi` crate (utoipa wrapper)
+  - Swagger UI embedding
+
+---
+
+## Usage Example (Current)
+
+```rust
+use rustapi_rs::prelude::*;
+
+#[derive(Serialize)]
+struct HelloResponse { message: String }
+
+async fn hello() -> Json<HelloResponse> {
+    Json(HelloResponse { message: "Hello!".into() })
+}
+
+#[tokio::main]
+async fn main() -> Result<(), Box<dyn std::error::Error + Send + Sync>> {
+    RustApi::new()
+        .route("/", get(hello))
+        .run("127.0.0.1:8080")
+        .await
+}
+```
+
+---
+
+## Target Usage (After Phase 2)
+
+```rust
+use rustapi_rs::prelude::*;
+
+#[derive(Schema, Validate, Deserialize)]
+struct RegisterRequest {
+    #[validate(email)]
+    email: String,
+    #[validate(length(min = 8))]
+    password: String,
+}
+
+#[derive(Schema, Serialize)]
+struct UserOut { id: i64, email: String }
+
+async fn register(body: ValidatedJson<RegisterRequest>) -> Result<Created<UserOut>> {
+    // body is already validated!
+    Ok(Created(UserOut { id: 1, email: body.email.clone() }))
+}
+
+#[tokio::main]
+async fn main() -> Result<(), Box<dyn std::error::Error + Send + Sync>> {
+    RustApi::new()
+        .route("/register", post(register))
+        .docs("/docs")        // Swagger UI
+        .openapi("/api.json") // OpenAPI spec
+        .run("127.0.0.1:8080")
+        .await
+}
+```
+
+---
+
+## Related Files
+
+| File | Purpose |
+|------|---------|
+| `README.md` | Full PRD and manifesto |
+| `memories/TASKLIST.md` | Detailed phase-by-phase tasks |
+| `memories/rustapi_memory_bank.md` | Technical reference |
+| `examples/hello-world/` | Working example |