Add per-project environment variable management as a first-class config
primitive. Env vars defined in .archon/config.yaml or stored in DB via
Web UI are merged into Options.env on Claude SDK calls.
Three env var sources merge in priority order (later wins):
1. process.env — global, from ~/.archon/.env via dotenv
2. .archon/config.yaml env: section — file-based per-project
3. DB remote_agent_codebase_env_vars table — Web UI per-project
Changes:
- Add remote_agent_codebase_env_vars table (PG migration + SQLite schema)
- Add DB CRUD module (packages/core/src/db/env-vars.ts)
- Extend IWorkflowStore with getCodebaseEnvVars method
- Add env field to RepoConfig, MergedConfig, WorkflowConfig, WorkflowAssistantOptions, AssistantRequestOptions
- Merge DB env vars in executor after config load
- Inject env vars into Claude subprocess via Options.env
- Add 3 API routes (GET/PUT/DELETE /api/codebases/:id/env)
- Add EnvVarsPanel to Settings page with masked value display
Fixes#852
