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/update.go

@@ -0,0 +1,30 @@
+package process
+
+import (
+	"context"
+	"fmt"
+
+	"connectrpc.com/connect"
+	"github.com/creack/pty"
+
+	rpc "git.omukk.dev/wrenn/sandbox/envd/internal/services/spec/process"
+)
+
+func (s *Service) Update(_ context.Context, req *connect.Request[rpc.UpdateRequest]) (*connect.Response[rpc.UpdateResponse], error) {
+	proc, err := s.getProcess(req.Msg.GetProcess())
+	if err != nil {
+		return nil, err
+	}
+
+	if req.Msg.GetPty() != nil {
+		err := proc.ResizeTty(&pty.Winsize{
+			Rows: uint16(req.Msg.GetPty().GetSize().GetRows()),
+			Cols: uint16(req.Msg.GetPty().GetSize().GetCols()),
+		})
+		if err != nil {
+			return nil, connect.NewError(connect.CodeInternal, fmt.Errorf("error resizing tty: %w", err))
+		}
+	}
+
+	return connect.NewResponse(&rpc.UpdateResponse{}), nil
+}