Initial commit: dial — interactive SSH host picker

A fast, read-only ~/.ssh/config picker that exec's the system ssh client.
Includes: static high-contrast picker with recency/frequency/name sort and
tag grouping, `dial keygen` (native ed25519/RSA + optional config entry), and
an optional offline YubiKey launch gate with one-time recovery codes.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

internal/connect/connect_unix.go

@@ -0,0 +1,21 @@
+//go:build !windows
+
+package connect
+
+import (
+	"os"
+	"os/exec"
+	"syscall"
+)
+
+// execCommand replaces the current process with the target binary via execve.
+// This is what makes ssh's tty/ProxyJump/agent-forwarding "just work": dial is
+// gone, and ssh owns the terminal directly with no wrapping parent.
+func execCommand(c Command) error {
+	path, err := exec.LookPath(c.Bin)
+	if err != nil {
+		return err
+	}
+	argv := append([]string{c.Bin}, c.Args...)
+	return syscall.Exec(path, argv, os.Environ())
+}