🤖 feat: add Docker runtime support

[ammar-agent]

Add Docker runtime for running workspaces in isolated containers.

Key Features

• One container per workspace: Container name derived from mux-{projectName}-{workspaceName}, sanitized for Docker's naming requirements
• Fixed paths inside container: /src for workspace, /tmp/mux-bashes for background processes
• Container lifecycle: Created on workspace creation, destroyed on deletion
• Project sync via git bundle: Similar to SSH - uses git bundle create locally, docker cp to transfer, then git clone from bundle inside container

Usage

/new my-feature -r docker ubuntu:22.04

This creates container mux-myproject-my-feature with workspace at /src.

Schema

Docker runtime config only requires:

{ type: "docker", image: string }

Changes

• DockerRuntime.ts: Main runtime implementation (~800 LoC) with exec, file operations, workspace management
• DockerRuntime.test.ts: Basic unit tests
• Schema: Added docker to RuntimeModeSchema enum
• Frontend: DockerIcon, runtime selector styles, globals.css color variables
• chatCommands: Parse docker <image> format
• systemMessage: Docker-specific environment context

Test Results

• make typecheck ✅
• make lint ✅
• bun test src/browser/utils/chatCommands.test.ts ✅ (23 tests)
• bun test src/node/runtime/DockerRuntime.test.ts ✅ (4 tests)
• bun test src/common src/browser ✅ (968 tests)

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Generated with mux

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