docs: add prereq script to setup instructions, check just + node

- Add 'just' and 'node' (>=20) to check-dev-prereqs.sh required checks
- Update README, CONTRIBUTING, AGENTS.md, CLAUDE.md to mention running
  'bash scripts/check-dev-prereqs.sh' before 'just setup' since just
  itself may not be installed yet

Author: pRizz

AGENTS.md

@@ -52,7 +52,7 @@ just run <args>  # Run CLI with arguments (e.g., just run status)
 just dev         # Start local runtime (local submodule + cached sandbox rebuild)
 ```
 
-Run `just setup` before any other project command after cloning this repo. In new worktrees, initialize the submodule first with `git submodule update --init --recursive`, then run `just setup`.
+Run `bash scripts/check-dev-prereqs.sh` to verify all required and optional tools are installed. Then run `just setup` before any other project command after cloning this repo. In new worktrees, initialize the submodule first with `git submodule update --init --recursive`, then run `just setup`.
 
 Setup reference:
 - Rust toolchain: `1.89` (from `rust-toolchain.toml`)

CLAUDE.md

@@ -52,7 +52,7 @@ just run <args>  # Run CLI with arguments (e.g., just run status)
 just dev         # Start local runtime (local submodule + cached sandbox rebuild)
 ```
 
-Run `just setup` before any other project command after cloning this repo. In new worktrees, initialize the submodule first with `git submodule update --init --recursive`, then run `just setup`.
+Run `bash scripts/check-dev-prereqs.sh` to verify all required and optional tools are installed. Then run `just setup` before any other project command after cloning this repo. In new worktrees, initialize the submodule first with `git submodule update --init --recursive`, then run `just setup`.
 
 Setup reference:
 - Rust toolchain: `1.89` (from `rust-toolchain.toml`)

CONTRIBUTING.md

@@ -33,8 +33,8 @@ git clone https://github.com/pRizz/opencode-cloud.git
 git clone https://gitea.com/pRizz/opencode-cloud.git
 cd opencode-cloud
 
-# Bun is required for this repo
-bun --version
+# Check prerequisites (can run before installing just)
+bash scripts/check-dev-prereqs.sh
 
 # First command after clone/worktree init (hooks + deps + submodule bootstrap)
 just setup

README.md

@@ -282,10 +282,10 @@ git clone https://github.com/pRizz/opencode-cloud.git
 git clone https://gitea.com/pRizz/opencode-cloud.git
 cd opencode-cloud
 
-# Bun is required for this repo
-bun --version
+# Check prerequisites (run this before anything else)
+bash scripts/check-dev-prereqs.sh
 
-# First command after clone/worktree init
+# First command after clone/worktree init (hooks + deps + submodule bootstrap)
 just setup
 just build
 just dev    # Recommended local dev start shortcut
@@ -587,6 +587,9 @@ Data (PID files, etc.) is stored at:
 - **Node.js 20+** — for the Node CLI wrapper
 
 ```bash
+# Check prerequisites (can run before installing just)
+bash scripts/check-dev-prereqs.sh
+
 # First command after clone/worktree init (hooks + deps + submodule bootstrap)
 just setup
 

scripts/check-dev-prereqs.sh

@@ -70,9 +70,25 @@ warn_if_missing() {
 echo "Checking development prerequisites..."
 
 require_command "git" "Install Git (https://git-scm.com/downloads)."
+require_command "just" "Install just: 'brew install just' or 'cargo install just' (https://github.com/casey/just)."
 require_command "bun" "Install Bun (https://bun.sh)."
 require_command "cargo" "Install Rust via rustup (https://rustup.rs)."
 require_command "rustc" "Install Rust via rustup (https://rustup.rs)."
+require_command "node" "Install Node.js 20+ (https://nodejs.org)."
+
+if command -v node >/dev/null 2>&1; then
+  node_raw="$(node --version | sed 's/^v//')"
+  node_version="$(version_parts_or_empty "$node_raw")"
+  if [[ -z "$node_version" ]]; then
+    print_error "Could not parse Node.js version from: $node_raw"
+    required_failures=$((required_failures + 1))
+  elif version_ge "$node_version" "20.0.0"; then
+    print_ok "node version $node_version >= 20.0.0"
+  else
+    print_error "node version $node_version is too old. Required: >= 20.0.0"
+    required_failures=$((required_failures + 1))
+  fi
+fi
 
 if command -v bun >/dev/null 2>&1; then
   bun_raw="$(bun --version | head -n1)"