feat: add custom environment variable configuration to rover.json

[Angelmmiguel]

Add support for custom environment variable configuration in rover.json, enabling projects to inject additional environment variables into AI agent containers. This feature introduces two optional properties: envs for explicit environment variable definitions and passthroughs, and envsFile for loading variables from dotenv files.

The custom environment variables are merged with agent-specific defaults and passed to Docker containers during task execution.

It closes #225

Changes

• Added envs and envsFile optional properties to ProjectConfigSchema with appropriate getters
• Bumped project schema version from 1.0 to 1.1 to support new configuration fields
• Created parseCustomEnvironmentVariables() utility function supporting both passthrough (ENV_NAME) and explicit value (ENV_NAME=VALUE) formats
• Created loadEnvsFile() utility function with path traversal validation and dotenv file parsing
• Modified startDockerExecution() in task command to load, parse, and merge custom environment variables with agent defaults
• Added dotenv package as a dependency for parsing dotenv files

Notes

Custom environment variables are appended after agent defaults when passed to Docker. When the same variable appears multiple times, Docker uses the last occurrence, allowing custom variables to override agent defaults.

Path traversal protection ensures envsFile paths are validated to stay within the project root directory. Invalid paths and missing files are silently skipped to maintain backwards compatibility.

Demo

I updated the project rover.json file to:

{
  "version": "1.1",
  "languages": [
    "javascript"
  ],
  "packageManagers": [
    "npm"
  ],
  "taskManagers": [],
  "attribution": true,
  "envs": [
    "STARSHIP_SHELL",
    "CUSTOM_VAR=test"
  ],
  "envsFile": ".env.rover"
}

Inside the container:

$ docker exec -it rover-task-74-1 bash
d04ab61b998a:/workspace$ env
CUSTOM_VAR=test
STARSHIP_SHELL=bash
ANOTHER_TEST=bye
THIS_IS_A_TEST=hello
...

[ereslibre]

LGTM, great feature!