Initial implementation of mcdeploy deployment tool

Single Go binary with five commands:
- build: podman build locally with registry tags + git version
- push: podman push to MCR
- deploy: SSH pull/stop/rm/run on target node
- cert renew: issue TLS cert from Metacrypt via REST API
- status: show container status on a node

Config-driven via TOML service registry describing images,
Dockerfiles, container configs per node. Shells out to podman
for container operations and ssh for remote access.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

exec.go

@@ -0,0 +1,64 @@
+package main
+
+import (
+	"bytes"
+	"fmt"
+	"os"
+	"os/exec"
+	"strings"
+)
+
+// run executes a local command, streaming stdout/stderr to os.Stdout/os.Stderr.
+func run(name string, args ...string) error {
+	fmt.Printf(">>> %s %s\n", name, strings.Join(args, " "))
+	cmd := exec.Command(name, args...)
+	cmd.Stdout = os.Stdout
+	cmd.Stderr = os.Stderr
+	return cmd.Run()
+}
+
+// runIn executes a local command in a specific directory.
+func runIn(dir string, name string, args ...string) error {
+	fmt.Printf(">>> (in %s) %s %s\n", dir, name, strings.Join(args, " "))
+	cmd := exec.Command(name, args...)
+	cmd.Dir = dir
+	cmd.Stdout = os.Stdout
+	cmd.Stderr = os.Stderr
+	return cmd.Run()
+}
+
+// runOutput executes a local command and returns stdout as a string.
+func runOutput(dir string, name string, args ...string) (string, error) {
+	fmt.Printf(">>> %s %s\n", name, strings.Join(args, " "))
+	cmd := exec.Command(name, args...)
+	cmd.Dir = dir
+	cmd.Stderr = os.Stderr
+	var buf bytes.Buffer
+	cmd.Stdout = &buf
+	if err := cmd.Run(); err != nil {
+		return "", err
+	}
+	return strings.TrimSpace(buf.String()), nil
+}
+
+// sshRun executes a command on a remote host via SSH.
+func sshRun(host string, command string) error {
+	fmt.Printf(">>> ssh %s %s\n", host, command)
+	cmd := exec.Command("ssh", host, command)
+	cmd.Stdout = os.Stdout
+	cmd.Stderr = os.Stderr
+	return cmd.Run()
+}
+
+// sshOutput executes a command on a remote host and returns stdout.
+func sshOutput(host string, command string) (string, error) {
+	fmt.Printf(">>> ssh %s %s\n", host, command)
+	cmd := exec.Command("ssh", host, command)
+	cmd.Stderr = os.Stderr
+	var buf bytes.Buffer
+	cmd.Stdout = &buf
+	if err := cmd.Run(); err != nil {
+		return "", err
+	}
+	return strings.TrimSpace(buf.String()), nil
+}