Remove duplicate proto files from envd/spec/ and update envd's
buf.gen.yaml to generate stubs from the canonical proto/envd/ location.
Both modules now generate their own Connect RPC stubs from the same
source protos.
- Copy envd source from e2b-dev/infra, internalize shared dependencies
into envd/internal/shared/ (keys, filesystem, id, smap, utils)
- Switch from gRPC to Connect RPC for all envd services
- Update module paths to git.omukk.dev/wrenn/{sandbox,sandbox/envd}
- Add proto specs (process, filesystem) with buf-based code generation
- Implement full envd: process exec, filesystem ops, port forwarding,
cgroup management, MMDS integration, and HTTP API
- Update main module dependencies (firecracker SDK, pgx, goose, etc.)
- Remove placeholder .gitkeep files replaced by real implementations
