docs: add CLAUDE.md for Claude Code guidance

CLAUDE.md

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+# CLAUDE.md
+
+This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.
+
+## Build Commands
+
+```bash
+cargo build                    # Debug build
+cargo build --release          # Release build
+cargo run                      # Run application
+cargo fmt --all                # Format code
+cargo clippy --all-features --all-targets -- -D warnings  # Lint (warnings as errors)
+```
+
+## Testing
+
+```bash
+cargo test --all-features --workspace              # All tests
+cargo test --doc --all-features --workspace        # Doc tests only
+cargo test <test_name> --all-features              # Single test
+cargo test --test kittest --all-features           # UI integration tests (egui_kittest)
+cargo test --test e2e --all-features               # End-to-end tests
+```
+
+Test locations:
+- Unit tests: inline in source files (`#[test]`)
+- UI integration: `tests/kittest/`
+- E2E: `tests/e2e/`
+
+## Architecture Overview
+
+**Dash Evo Tool** is a cross-platform GUI application (Rust + egui) for interacting with Dash Evolution. It enables DPNS username registration, contest voting, state transition viewing, wallet management, and identity operations across Mainnet/Testnet/Devnet.
+
+### Core Module Structure
+
+- **app.rs** - Main application state, task result handling, screen management
+- **ui/** - Screens (network_chooser, dpns, identities, wallets, contracts_documents, tokens, dashpay, tools) and reusable components
+- **backend_task/** - Async business logic (contract, document, platform_info, identity, wallet operations)
+- **model/** - Data types (amounts, fees, settings, wallet/identity models)
+- **database/** - SQLite persistence (rusqlite) for wallets, identities, settings, proof logs
+- **context.rs** - Application context (network config, SDK client, database connection)
+- **spv/** - Simplified Payment Verification for light wallet support
+- **components/core_zmq_listener** - Real-time Dash Core event listening
+
+### Key Dependencies
+
+- `dash-sdk` - Dash blockchain SDK (platform protocol, core interactions)
+- `egui/eframe` - Immediate mode GUI framework
+- `tokio` - Async runtime (12 worker threads)
+- `rusqlite` - SQLite with bundled library
+
+### Configuration
+
+Environment config via `.env` in app directory:
+- macOS: `~/Library/Application Support/Dash-Evo-Tool/.env`
+- Linux: `~/.config/dash-evo-tool/.env`
+- Windows: `C:\Users\<User>\AppData\Roaming\Dash-Evo-Tool\config\.env`
+
+See `.env.example` for network configuration options.
+
+## UI Component Pattern
+
+Components follow a lazy initialization pattern (see `doc/COMPONENT_DESIGN_PATTERN.md`):
+
+```rust
+struct MyScreen {
+    amount: Option<Amount>,              // Domain data
+    amount_widget: Option<AmountInput>,  // UI component (lazy)
+}
+
+// In show():
+let widget = self.amount_widget.get_or_insert_with(|| AmountInput::new(type));
+let response = widget.show(ui);
+response.inner.update(&mut self.amount);
+```
+
+**Requirements:**
+- Private fields only
+- Builder methods for configuration (`with_label()`, etc.)
+- Response struct with `ComponentResponse` trait
+- Self-contained validation and error handling
+- Support both light and dark mode via `ComponentStyles`
+
+**Anti-patterns:** public mutable fields, eager initialization, not clearing invalid data
+
+## Platform Targets
+
+Linux (x86_64/aarch64), Windows (x86_64), macOS (x86_64/aarch64 with code signing)
+
+Requires protoc v25.2+ for protocol buffer compilation.