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/host/metrics.go

@@ -0,0 +1,93 @@
+package host
+
+import (
+	"math"
+	"time"
+
+	"github.com/shirou/gopsutil/v4/cpu"
+	"github.com/shirou/gopsutil/v4/mem"
+	"golang.org/x/sys/unix"
+)
+
+type Metrics struct {
+	Timestamp int64 `json:"ts"` // Unix Timestamp in UTC
+
+	CPUCount       uint32  `json:"cpu_count"`    // Total CPU cores
+	CPUUsedPercent float32 `json:"cpu_used_pct"` // Percent rounded to 2 decimal places
+
+	// Deprecated: kept for backwards compatibility with older orchestrators.
+	MemTotalMiB uint64 `json:"mem_total_mib"` // Total virtual memory in MiB
+
+	// Deprecated: kept for backwards compatibility with older orchestrators.
+	MemUsedMiB uint64 `json:"mem_used_mib"` // Used virtual memory in MiB
+
+	MemTotal uint64 `json:"mem_total"` // Total virtual memory in bytes
+	MemUsed  uint64 `json:"mem_used"`  // Used virtual memory in bytes
+
+	DiskUsed  uint64 `json:"disk_used"`  // Used disk space in bytes
+	DiskTotal uint64 `json:"disk_total"` // Total disk space in bytes
+}
+
+func GetMetrics() (*Metrics, error) {
+	v, err := mem.VirtualMemory()
+	if err != nil {
+		return nil, err
+	}
+
+	memUsedMiB := v.Used / 1024 / 1024
+	memTotalMiB := v.Total / 1024 / 1024
+
+	cpuTotal, err := cpu.Counts(true)
+	if err != nil {
+		return nil, err
+	}
+
+	cpuUsedPcts, err := cpu.Percent(0, false)
+	if err != nil {
+		return nil, err
+	}
+
+	cpuUsedPct := cpuUsedPcts[0]
+	cpuUsedPctRounded := float32(cpuUsedPct)
+	if cpuUsedPct > 0 {
+		cpuUsedPctRounded = float32(math.Round(cpuUsedPct*100) / 100)
+	}
+
+	diskMetrics, err := diskStats("/")
+	if err != nil {
+		return nil, err
+	}
+
+	return &Metrics{
+		Timestamp:      time.Now().UTC().Unix(),
+		CPUCount:       uint32(cpuTotal),
+		CPUUsedPercent: cpuUsedPctRounded,
+		MemUsedMiB:     memUsedMiB,
+		MemTotalMiB:    memTotalMiB,
+		MemTotal:       v.Total,
+		MemUsed:        v.Used,
+		DiskUsed:       diskMetrics.Total - diskMetrics.Available,
+		DiskTotal:      diskMetrics.Total,
+	}, nil
+}
+
+type diskSpace struct {
+	Total     uint64
+	Available uint64
+}
+
+func diskStats(path string) (diskSpace, error) {
+	var st unix.Statfs_t
+	if err := unix.Statfs(path, &st); err != nil {
+		return diskSpace{}, err
+	}
+
+	block := uint64(st.Bsize)
+
+	// all data blocks
+	total := st.Blocks * block
+	// blocks available
+	available := st.Bavail * block
+
+	return diskSpace{Total: total, Available: available}, nil
+}