Port envd from e2b with internalized shared packages and Connect RPC

- 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

envd/internal/services/process/list.go

@@ -0,0 +1,28 @@
+package process
+
+import (
+	"context"
+
+	"connectrpc.com/connect"
+
+	"git.omukk.dev/wrenn/sandbox/envd/internal/services/process/handler"
+	rpc "git.omukk.dev/wrenn/sandbox/envd/internal/services/spec/process"
+)
+
+func (s *Service) List(context.Context, *connect.Request[rpc.ListRequest]) (*connect.Response[rpc.ListResponse], error) {
+	processes := make([]*rpc.ProcessInfo, 0)
+
+	s.processes.Range(func(pid uint32, value *handler.Handler) bool {
+		processes = append(processes, &rpc.ProcessInfo{
+			Pid:    pid,
+			Tag:    value.Tag,
+			Config: value.Config,
+		})
+
+		return true
+	})
+
+	return connect.NewResponse(&rpc.ListResponse{
+		Processes: processes,
+	}), nil
+}