🤖 Add SSH runtime with integration tests

Implements SSHRuntime for executing commands and file operations on remote
hosts via SSH, enabling distributed agent workspaces.

**Implementation:**

- Uses system `ssh` command (respects ~/.ssh/config, ProxyJump, ControlMaster)
- Supports SSH config aliases, custom ports, identity files
- Opportunistic rsync with tar+ssh fallback for file sync
- Web Streams for stdout/stderr with proper async handling
- 300s timeout for long-running operations

**Workspace Creation:**

- createWorkspace() syncs project via rsync/tar+ssh
- Remote git checkout on target branch
- Runs .cmux/init hooks remotely
- Returns remote workspace path

**Testing:**

- Docker-based SSH server fixture (Alpine Linux)
- Integration tests for LocalRuntime and SSHRuntime
- Tests workspace creation, file I/O, command execution
- SSH tests automatically skipped in CI (requires Docker)

**Configuration:**

- WorkspaceMetadata extended with optional runtime config
- Runtime created via runtimeFactory based on config
- Falls back to LocalRuntime if no config specified

Generated with `cmux`

Author: ammar-agent

bun.lock

@@ -110,7 +110,7 @@ Verify with React DevTools Profiler - MarkdownCore should only re-render when co
 
 ## Documentation Guidelines
 
-**Free-floating markdown docs are not permitted.** Documentation must be organized:
+**Free-floating markdown docs are not permitted.** Documentation must be organized. Do not create standalone markdown files in the project root or random locations, even for implementation summaries or planning documents - use the propose_plan tool or inline comments instead.
 
 - **User-facing docs** → `./docs/` directory
   - **IMPORTANT**: Read `docs/README.md` first before writing user-facing documentation
@@ -119,6 +119,7 @@ Verify with React DevTools Profiler - MarkdownCore should only re-render when co
   - Use standard markdown + mermaid diagrams
 - **Developer docs** → inline with the code its documenting as comments. Consider them notes as notes to future Assistants to understand the logic more quickly.
   **DO NOT** create standalone documentation files in the project root or random locations.
+- **Test documentation** → inline comments in test files explaining complex test setup or edge cases, NOT separate README files.
 
 **NEVER create markdown documentation files (README, guides, summaries, etc.) in the project root during feature development unless the user explicitly requests documentation.** Code + tests + inline comments are complete documentation.
 

docs/AGENTS.md

@@ -41,7 +41,8 @@
     "docs:watch": "make docs-watch",
     "storybook": "make storybook",
     "storybook:build": "make storybook-build",
-    "test:storybook": "make test-storybook"
+    "test:storybook": "make test-storybook",
+    "rebuild": "echo \"No native modules to rebuild\""
   },
   "dependencies": {
     "@ai-sdk/anthropic": "^2.0.29",