fix(api,watcher): name the queue, list parked non-markdown, reserved wings, top-level-only frontmatter key; document the inbox (review of #211)

- brain_promote/brain_reject take an optional queue (inbox | needs-review); a
  name present in both is refused instead of silently acting on the top-level
  note; brain_pending labels every entry with its queue
- parked pdf/txt files are listed (they were invisible); only markdown can be
  promoted, the others are moved or rejected
- promote refuses sources/concepts/entities/wiki as a wing
- frontmatterWing reads only a top-level key inside a properly fenced block
- docs/raw-inbox.md: the contract, the three env vars, the known limits
Each behaviour has a test that fails without it (mutation-checked).

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

ingestion/internal/watcher/watcher.go

@@ -392,14 +392,23 @@ func topDir(rel string) string {
 	return ""
 }
 
-// frontmatterWing reads `wing:` from a note's leading frontmatter, "" if none.
+// frontmatterWing reads a top-level `wing:` from a note's leading frontmatter,
+// "" if there is none. The block counts only if it has a real closing fence (a
+// line that is exactly "---"), and an indented `wing:` belongs to some other
+// mapping, not to the note.
 func frontmatterWing(content string) string {
 	content = strings.ReplaceAll(content, "\r\n", "\n")
 	if !strings.HasPrefix(content, "---\n") {
 		return ""
 	}
-	block, _, _ := strings.Cut(content[4:], "\n---")
+	block, _, found := cutFence(content[4:])
+	if !found {
+		return ""
+	}
 	for _, line := range strings.Split(block, "\n") {
+		if line == "" || line[0] == ' ' || line[0] == '\t' {
+			continue
+		}
 		if key, val, ok := strings.Cut(line, ":"); ok && strings.TrimSpace(key) == "wing" {
 			return strings.Trim(strings.TrimSpace(val), `"'`)
 		}