feat(embedded): add Perses + VictoriaMetrics subprocess management with auto-download

Ultraworked with [Sisyphus](https://github.com/code-yeongyu/claude-agent)

Co-authored-by: Sisyphus <clio-agent@sisyphuslabs.ai>

internal/embedded/vm.go

@@ -0,0 +1,88 @@
+package embedded
+
+import (
+	"fmt"
+	"os"
+	"os/exec"
+	"path/filepath"
+
+	"github.com/fujin/anthropic-proxy/internal/config"
+	"github.com/rs/zerolog/log"
+)
+
+type VM struct {
+	cfg       config.EmbeddedConfig
+	proxyPort int
+	cmd       *exec.Cmd
+	tmpDir    string
+}
+
+func NewVM(cfg config.EmbeddedConfig, proxyPort int) *VM {
+	return &VM{cfg: cfg, proxyPort: proxyPort}
+}
+
+func (v *VM) Start() error {
+	bin, err := ensureBinary("victoria-metrics", v.cfg.VMBinary, v.cfg.BinDir)
+	if err != nil {
+		return fmt.Errorf("victoria-metrics: %w", err)
+	}
+
+	v.tmpDir, err = os.MkdirTemp("", "vm-*")
+	if err != nil {
+		return fmt.Errorf("create temp dir: %w", err)
+	}
+
+	scrapeConfig := fmt.Sprintf(`global:
+  scrape_interval: 15s
+scrape_configs:
+  - job_name: anthropic-proxy
+    static_configs:
+      - targets:
+          - localhost:%d
+`, v.proxyPort)
+
+	scrapePath := filepath.Join(v.tmpDir, "scrape.yaml")
+	if err := os.WriteFile(scrapePath, []byte(scrapeConfig), 0o644); err != nil {
+		return fmt.Errorf("write scrape config: %w", err)
+	}
+
+	dataPath := filepath.Join(v.tmpDir, "data")
+	if err := os.MkdirAll(dataPath, 0o755); err != nil {
+		return fmt.Errorf("create data dir: %w", err)
+	}
+
+	v.cmd = exec.Command(bin,
+		"-storageDataPath", dataPath,
+		"-retentionPeriod", "7d",
+		"-httpListenAddr", fmt.Sprintf(":%d", v.cfg.VMPort),
+		"-promscrape.config", scrapePath,
+	)
+	v.cmd.Stdout = &logWriter{level: "info", component: "victoria-metrics"}
+	v.cmd.Stderr = &logWriter{level: "error", component: "victoria-metrics"}
+
+	if err := v.cmd.Start(); err != nil {
+		return fmt.Errorf("start victoria-metrics: %w", err)
+	}
+
+	log.Info().
+		Str("binary", bin).
+		Int("port", v.cfg.VMPort).
+		Int("scrape_target_port", v.proxyPort).
+		Msg("victoria-metrics started")
+
+	return nil
+}
+
+func (v *VM) Stop() {
+	if v.cmd != nil && v.cmd.Process != nil {
+		_ = v.cmd.Process.Kill()
+		_ = v.cmd.Wait()
+	}
+	if v.tmpDir != "" {
+		_ = os.RemoveAll(v.tmpDir)
+	}
+}
+
+func (v *VM) Running() bool {
+	return v.cmd != nil && v.cmd.Process != nil && v.cmd.ProcessState == nil
+}