docs: ci and mintd build (#1538)

* docs: add self hosted docs

* chore: add nix build for mintd

DEVELOPMENT.md

@@ -366,6 +366,28 @@ Not all changes should be backported to stable branches. **Don't add backport la
 
 If a backport isn't appropriate, simply don't add the backport label to the PR.
 
+## CI & Infrastructure
+
+CDK uses a specialized self-hosted infrastructure for CI/CD, specifically for fuzzing and integration tests.
+
+### Self-Hosted Runners
+
+Our infrastructure is defined in the [cdk-infra](https://github.com/thesimplekid/cdk-infra) repository. It utilizes a "warm pool" of ephemeral NixOS containers to provide reproducible, isolated, and high-performance runners.
+
+**Key Features:**
+- **Ephemeral:** Each job runs in a fresh, ephemeral NixOS container that is destroyed immediately after use.
+- **Warm Pool:** Containers are pre-provisioned to ensure instant job pickup.
+- **Nix Native:** Fully supports Nix builds and caching.
+- **Isolation:** Runners are network-isolated for security.
+
+### Architecture
+
+The system consists of:
+- **Runners:** Two dedicated hosts (`cdk-runner-01` and `cdk-runner-02`) running NixOS.
+- **Controller:** A custom Rust controller manages the lifecycle of the containers, monitoring the repository for queued jobs and maintaining the warm pool.
+
+For more details on the infrastructure implementation, deployment, and management, please refer to the [cdk-infra repository](https://github.com/thesimplekid/cdk-infra).
+
 ## Additional Resources
 
 - [Nix Documentation](https://nixos.org/manual/nix/stable/)

crates/cdk-mintd/README.md

@@ -31,9 +31,17 @@ For detailed configuration of each Lightning backend, see:
 Download the latest release from the [GitHub releases page](https://github.com/cashubtc/cdk/releases).
 
 ### Option 2: Build from Source
+
+This project uses [Nix](https://nixos.org/) to manage development dependencies.
+
 ```bash
 git clone https://github.com/cashubtc/cdk.git
 cd cdk
+
+# Enter development environment
+nix develop
+
+# Build binary
 cargo build --bin cdk-mintd --release
 # Binary will be at ./target/release/cdk-mintd
 ```