feat: markdown import splits H2 leafs in Go

Drop the Python ExecFile wrapper. Conversion still does not write
Ladybug; add a dry-run fixture check for the index adapter split.

bin/markdown/import.go

@@ -1,20 +1,100 @@
-//usr/bin/env go run -tags=markdown_import "$0" "$@"; exit
-//go:build markdown_import
+//usr/bin/env go run "$0" "$@"; exit
 //
-// bin/markdown/import.go - split markdown into leafs (mistune).
+// bin/markdown/import.go - split markdown into leafs (H2 boundaries).
 //
 //	./bin/markdown/import.go [dir]
 //	./bin/markdown/import.go --files a.md,b.md --json
 //
+// Conversion only. Brain write is bin/brain/index.go.
+// Python bin/md/import remains as a fallback.
 // NOTE: never run `gofmt -w` on this file — it breaks the shebang.
 package main
 
 import (
+	"fmt"
 	"os"
+	"strings"
 
-	"github.com/eSlider/2dph/internal/cmdbin"
+	"github.com/eSlider/2dph/internal/mdleaves"
 )
 
 func main() {
-	os.Exit(cmdbin.ExecFile("bin/md/import", os.Args[1:]))
+	os.Exit(run(os.Args[1:]))
+}
+
+func run(args []string) int {
+	jsonOut := false
+	files := ""
+	root := "."
+	for i := 0; i < len(args); i++ {
+		a := args[i]
+		switch {
+		case a == "--json":
+			jsonOut = true
+		case a == "--files" && i+1 < len(args):
+			i++
+			files = args[i]
+		case strings.HasPrefix(a, "--files="):
+			files = strings.TrimPrefix(a, "--files=")
+		case a == "-h" || a == "--help":
+			fmt.Fprintln(os.Stderr, "bin/markdown/import.go [dir] [--files a.md,b.md] [--json]")
+			return 0
+		case strings.HasPrefix(a, "-"):
+			fmt.Fprintln(os.Stderr, "unknown arg:", a)
+			return 2
+		default:
+			root = a
+		}
+	}
+
+	var paths []string
+	if files != "" {
+		for _, f := range strings.Split(files, ",") {
+			f = strings.TrimSpace(f)
+			if f != "" {
+				paths = append(paths, f)
+			}
+		}
+	} else {
+		st, err := os.Stat(root)
+		if err != nil {
+			fmt.Fprintf(os.Stderr, "md/import: no such path %s\n", root)
+			return 2
+		}
+		if !st.IsDir() {
+			paths = []string{root}
+		} else {
+			var err error
+			paths, err = mdleaves.WalkMarkdown(root)
+			if err != nil {
+				fmt.Fprintf(os.Stderr, "md/import: %v\n", err)
+				return 1
+			}
+		}
+	}
+	if len(paths) == 0 {
+		fmt.Fprintln(os.Stderr, "md/import: no markdown files")
+		return 1
+	}
+
+	var all []mdleaves.Leaf
+	for _, p := range paths {
+		raw, err := os.ReadFile(p)
+		if err != nil {
+			fmt.Fprintf(os.Stderr, "md/import: %s: %v\n", p, err)
+			continue
+		}
+		all = append(all, mdleaves.ToAll(string(raw), p, "")...)
+	}
+	if jsonOut {
+		s, err := mdleaves.EncodeJSON(all)
+		if err != nil {
+			fmt.Fprintln(os.Stderr, err)
+			return 1
+		}
+		fmt.Print(s)
+		return 0
+	}
+	fmt.Print(mdleaves.EncodeYAML(all))
+	return 0
 }