fix: gateway instructions (#421)

Adds the complete steps for the gateway setup guide

Author: sarahschwartz

content/10.zk-stack/20.running/25.gateway-settlement-layer.md

@@ -11,9 +11,40 @@ enhance **interoperability**, provide **proof aggregation**, and offer **cost ef
 ## Running ZKsync Gateway locally
 
 ::callout{icon="i-heroicons-exclamation-triangle" color="amber"}
-This guide assumes you already have an ecosystem with a ZKsync chain settling on L1 [as detailed in the quickstart](./quickstart).
+This guide assumes you already have `zkstackup` and the required system dependencies installed [as detailed in the quickstart](./quickstart).
 ::
 
+1. Update `foundry-zksync` to use the version from commit `27360d4c8`:
+
+    ```bash
+    foundryup-zksync -C 27360d4c8
+    ```
+
+1. Clone the `zksync-era` repository,
+  update the `contracts` submodule,
+  install the latest version of `zkstack`:
+
+    ```bash
+    git clone https://github.com/matter-labs/zksync-era.git
+    cd zksync-era
+    git submodule update --init --recursive
+    zkstackup --local
+    zkstack dev clean all
+    ```
+
+1. Start the containers and initialize the ecosystem:
+
+    ```bash
+    zkstack containers
+    zkstack ecosystem init --deploy-paymaster --deploy-erc20 \
+    --deploy-ecosystem --l1-rpc-url=http://localhost:8545 \
+    --server-db-url=postgres://postgres:notsecurepassword@localhost:5432 \
+    --server-db-name=zksync_server_localhost_era \
+    --ignore-prerequisites --observability=false \
+    --chain era \
+    --update-submodules false
+    ```
+
 1. Create a new ZKsync chain that will become your local gateway chain:
 
     ```bash
@@ -53,20 +84,26 @@ This guide assumes you already have an ecosystem with a ZKsync chain settling on
     ```bash
     mkdir zlogs
     zkstack server --ignore-prerequisites --chain gateway &> ./zlogs/gateway.log &
+    zkstack server wait --ignore-prerequisites --verbose --chain gateway
     ```
 
 1. Migrate existing ZKsync chain to settle on `gateway`:
 
     ```bash
-    zkstack chain gateway migrate-to-gateway --chain YOUR_CHAIN_NAME --gateway-chain-name gateway
+    zkstack chain gateway migrate-to-gateway --chain era --gateway-chain-name gateway
     ```
 
 1. Start your chain server:
 
     ```bash
-    zkstack server --ignore-prerequisites --chain YOUR_CHAIN &> ./era.log &
+    zkstack server --ignore-prerequisites --chain era &> ./era.log &
     ```
 
+Your chains will be running on the following ports:
+
+- Era (271): `localhost:3050`
+- Gateway (506): `localhost:3150`
+
 ## Migrate existing ZKsync chain to Gateway on testnet or mainnet
 
 ZKsync chains can be migrated to use ZKsync Gateway as their settlement layer by updating the chain's metadata and