Add rustup for on-demand Rust support, document JS/TS development

Install rustup-init binary from Rust CDN. Users bootstrap Rust with
'rustup-init -y' — persists via devbox-rustup and devbox-cargo volumes.
Add JavaScript/TypeScript development docs (Node.js + npm in base, Bun in OMOS).

DOCKER_HUB.md

@@ -185,6 +185,8 @@ Understanding what survives container restarts and what doesn't:
 | `/home/developer/.aws` | Host bind mount | ✅ Yes — lives on host | AWS credentials/SSO cache |
 | `/home/developer/.local/share/opencode` | Named volume (if configured) | ✅ Yes — Docker volume | Session history, memory, auth tokens |
 | `/home/developer/.local/share/uv` | Named volume (if configured) | ✅ Yes — Docker volume | Python installs, uv tool installs |
+| `/home/developer/.rustup` | Named volume (if configured) | ✅ Yes — Docker volume | Rust toolchains |
+| `/home/developer/.cargo` | Named volume (if configured) | ✅ Yes — Docker volume | Cargo binaries, registry cache |
 | `/home/developer/.config/opencode` | Host bind mount (if configured) | ✅ Yes — lives on host | opencode.json, oh-my-opencode-slim.json, skills |
 
 ### Key points
@@ -193,6 +195,7 @@ Understanding what survives container restarts and what doesn't:
 - **opencode config** is auto-generated from `OPENCODE_PROVIDER` env var on each start if no existing config is found. To persist config changes, mount the config directory from the host (see Custom opencode Config below).
 - **opencode data** (session history, memory) is lost with `--rm` unless you add a named volume.
 - **Python installs** via `uv python install` are lost unless you add the `devbox-uv` named volume.
+- **Rust toolchains** via `rustup-init` are lost unless you add the `devbox-rustup` and `devbox-cargo` named volumes.
 - **AWS SSO tokens** persist across restarts when `~/.aws` is mounted (recommended for Bedrock users).
 
 ## Custom opencode Config
@@ -252,6 +255,56 @@ docker run -it --rm \
 
 Project virtual environments (`.venv`) are stored in your workspace directory and persist automatically via the `/workspace` bind mount.
 
+## Rust Development with rustup
+
+The image includes `rustup-init`, the Rust toolchain installer. Rust is not pre-installed but can be bootstrapped on demand:
+
+```bash
+# One-time setup: install Rust toolchain (~300MB, persists with volumes)
+rustup-init -y
+source ~/.cargo/env
+
+# Now use Rust normally
+cargo new my-project
+cargo build
+cargo run
+```
+
+To persist Rust toolchains and cargo data across container restarts, add named volumes:
+
+```bash
+docker run -it --rm \
+  -v devbox-rustup:/home/developer/.rustup \
+  -v devbox-cargo:/home/developer/.cargo \
+  ... \
+  joakimp/opencode-devbox:latest
+```
+
+## JavaScript and TypeScript
+
+The base image includes **Node.js 22** and **npm** — sufficient for most JavaScript and TypeScript development:
+
+```bash
+# Initialize a new project
+npm init -y
+
+# Install dependencies
+npm install
+
+# Run TypeScript (via tsx, ts-node, etc.)
+npx tsx src/index.ts
+```
+
+The OMOS image variant also includes **Bun**, a faster JavaScript runtime and package manager:
+
+```bash
+bun init
+bun install
+bun run src/index.ts
+```
+
+Node modules are stored in your project directory under `/workspace` and persist automatically.
+
 ## Using docker-compose
 
 Create a directory with a `docker-compose.yml` and a `.env` file:
@@ -291,6 +344,9 @@ services:
       - devbox-data:/home/developer/.local/share/opencode
       # Optional: persist Python/uv installs across restarts
       # - devbox-uv:/home/developer/.local/share/uv
+      # Optional: persist Rust toolchains and cargo data
+      # - devbox-rustup:/home/developer/.rustup
+      # - devbox-cargo:/home/developer/.cargo
       # Mount AWS config for Bedrock SSO (required for amazon-bedrock provider)
       # - ~/.aws:/home/developer/.aws
       # Optional: mount opencode config directory (persists config changes across restarts)
@@ -303,6 +359,8 @@ services:
 volumes:
   devbox-data:
   # devbox-uv:
+  # devbox-rustup:
+  # devbox-cargo:
 ```
 
 Docker Compose loads `.env` automatically from the same directory. All variables from `.env` are passed to the container via `env_file`. Do **not** hardcode provider settings in the `environment:` section — use `.env` instead.
@@ -336,7 +394,7 @@ docker compose run --rm devbox bash   # interactive shell
 - **opencode** — AI coding assistant
 - **Node.js 22** — for npx-based MCP servers
 - **AWS CLI v2** — SSO and Bedrock authentication
-- **Dev tools** — git, git-lfs, ssh, ripgrep, fd, fzf, bat, eza, zoxide, uv, jq, make, curl, wget, neovim 0.12, tmux, htop, tree
+- **Dev tools** — git, git-lfs, ssh, ripgrep, fd, fzf, bat, eza, zoxide, uv, rustup, jq, make, curl, wget, neovim 0.12, tmux, htop, tree
 - **Non-root user** — runs as `developer` with UID auto-matched to workspace owner (sudo available)
 
 ### OMOS image (`latest-omos`)