feat: support rich multi-paragraph notes with formatting (Closes #7)

Add {start_of_notes}/{end_of_notes} (and short forms {son}/{eon}) block
directives to ChordProParser for multi-paragraph note content. Blank lines
within the block separate paragraphs. The renderer now word-wraps note
paragraphs to fit within the content width. MeasurementEngine estimates
wrapped line count for more accurate height calculations.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

renderer-pdf/src/main/kotlin/de/pfadfinder/songbook/renderer/pdf/PdfBookRenderer.kt

@@ -226,19 +226,28 @@ class PdfBookRenderer : BookRenderer {
             y -= config.layout.verseSpacing / 0.3528f
         }
 
-        // Render notes at the bottom
+        // Render notes at the bottom (with word-wrap for multi-paragraph notes)
         if (pageIndex == 0 && song.notes.isNotEmpty()) {
             y -= 4f
             val metaFont = fontMetrics.getBaseFont(config.fonts.metadata)
             val metaSize = config.fonts.metadata.size
-            for (note in song.notes) {
-                cb.beginText()
-                cb.setFontAndSize(metaFont, metaSize)
-                cb.setColorFill(Color.GRAY)
-                cb.setTextMatrix(leftMargin, y - metaSize)
-                cb.showText(note)
-                cb.endText()
-                y -= metaSize * 1.5f
+            val noteLineHeight = metaSize * 1.5f
+
+            for ((idx, note) in song.notes.withIndex()) {
+                val wrappedLines = wrapText(note, metaFont, metaSize, contentWidth)
+                for (wrappedLine in wrappedLines) {
+                    cb.beginText()
+                    cb.setFontAndSize(metaFont, metaSize)
+                    cb.setColorFill(Color.GRAY)
+                    cb.setTextMatrix(leftMargin, y - metaSize)
+                    cb.showText(wrappedLine)
+                    cb.endText()
+                    y -= noteLineHeight
+                }
+                // Add paragraph spacing between note paragraphs
+                if (idx < song.notes.size - 1) {
+                    y -= noteLineHeight * 0.3f
+                }
             }
         }