feat(workspace): numbered lists and reliable markdown paste

- block type 'numbered' (/number): 1., a., i. by nesting, continues on
  Enter, an empty item ends the list; markdown export/import as 1.
- pasting: parser moved to lib/pasteOutline with tests; blank lines split
  paragraphs, numbered lists keep their type, indentation levels follow
  the widths in use (2, 3 or 4 spaces, tabs)
- text that stays in the focused block after pasting (a paragraph with
  line breaks) was dropped; the block now takes it

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

internal/storage/import_markdown.go

@@ -824,6 +824,9 @@ func MarkdownToBlocks(md string) []domain.DocumentBlock {
 			level := listLevel(indentWidth(m[1]))
 			content := m[2]
 			typ := "bullet"
+			if t := strings.TrimLeft(line, " \t"); t != "" && t[0] >= '0' && t[0] <= '9' {
+				typ = "numbered"
+			}
 			checked := false
 			if c := checkboxRe.FindStringSubmatch(content); c != nil {
 				typ, checked, content = "todo", c[1] != " ", c[2]