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>

parser/src/main/kotlin/de/pfadfinder/songbook/parser/ChordProParser.kt

@@ -25,6 +25,17 @@ object ChordProParser {
         var currentLabel: String? = null
         var currentLines = mutableListOf<SongLine>()
 
+        // Notes block state
+        var inNotesBlock = false
+        var currentNoteParagraph = StringBuilder()
+
+        fun flushNoteParagraph() {
+            if (currentNoteParagraph.isNotEmpty()) {
+                notes.add(currentNoteParagraph.toString().trim())
+                currentNoteParagraph = StringBuilder()
+            }
+        }
+
         fun flushSection() {
             if (currentType != null) {
                 sections.add(SongSection(type = currentType!!, label = currentLabel, lines = currentLines.toList()))
@@ -37,6 +48,27 @@ object ChordProParser {
         for (rawLine in lines) {
             val line = rawLine.trimEnd()
 
+            // Inside a notes block: collect lines as paragraphs
+            if (inNotesBlock) {
+                if (line.trimStart().startsWith("{") && line.trimEnd().endsWith("}")) {
+                    val inner = line.trim().removePrefix("{").removeSuffix("}").trim().lowercase()
+                    if (inner == "end_of_notes" || inner == "eon") {
+                        flushNoteParagraph()
+                        inNotesBlock = false
+                        continue
+                    }
+                }
+                if (line.isBlank()) {
+                    flushNoteParagraph()
+                } else {
+                    if (currentNoteParagraph.isNotEmpty()) {
+                        currentNoteParagraph.append(" ")
+                    }
+                    currentNoteParagraph.append(line.trim())
+                }
+                continue
+            }
+
             // Skip comments
             if (line.trimStart().startsWith("#")) continue
 
@@ -97,6 +129,14 @@ object ChordProParser {
                     "end_of_repeat", "eor" -> {
                         flushSection()
                     }
+                    "start_of_notes", "son" -> {
+                        inNotesBlock = true
+                    }
+                    "end_of_notes", "eon" -> {
+                        // Should have been handled in the notes block above
+                        flushNoteParagraph()
+                        inNotesBlock = false
+                    }
                     "chorus" -> {
                         flushSection()
                         sections.add(SongSection(type = SectionType.CHORUS))

parser/src/test/kotlin/de/pfadfinder/songbook/parser/ChordProParserTest.kt

@@ -485,4 +485,96 @@ class ChordProParserTest {
         line.segments[2].chord shouldBe "G"
         line.segments[2].text shouldBe "End"
     }
+
+    @Test
+    fun `parse notes block with multiple paragraphs`() {
+        val input = """
+            {title: Song}
+            {start_of_notes}
+            First paragraph of the notes.
+            It continues on the next line.
+
+            Second paragraph with different content.
+            {end_of_notes}
+            {start_of_verse}
+            text
+            {end_of_verse}
+        """.trimIndent()
+        val song = ChordProParser.parse(input)
+        song.notes shouldHaveSize 2
+        song.notes[0] shouldBe "First paragraph of the notes. It continues on the next line."
+        song.notes[1] shouldBe "Second paragraph with different content."
+    }
+
+    @Test
+    fun `parse notes block with single paragraph`() {
+        val input = """
+            {title: Song}
+            {start_of_notes}
+            A single note paragraph.
+            {end_of_notes}
+            {start_of_verse}
+            text
+            {end_of_verse}
+        """.trimIndent()
+        val song = ChordProParser.parse(input)
+        song.notes shouldHaveSize 1
+        song.notes[0] shouldBe "A single note paragraph."
+    }
+
+    @Test
+    fun `parse notes block with short directives son eon`() {
+        val input = """
+            {title: Song}
+            {son}
+            Short form notes.
+            {eon}
+            {start_of_verse}
+            text
+            {end_of_verse}
+        """.trimIndent()
+        val song = ChordProParser.parse(input)
+        song.notes shouldHaveSize 1
+        song.notes[0] shouldBe "Short form notes."
+    }
+
+    @Test
+    fun `notes block and single note directives combine`() {
+        val input = """
+            {title: Song}
+            {note: Single line note}
+            {start_of_notes}
+            Block note paragraph.
+            {end_of_notes}
+            {start_of_verse}
+            text
+            {end_of_verse}
+        """.trimIndent()
+        val song = ChordProParser.parse(input)
+        song.notes shouldHaveSize 2
+        song.notes[0] shouldBe "Single line note"
+        song.notes[1] shouldBe "Block note paragraph."
+    }
+
+    @Test
+    fun `parse notes block with three paragraphs`() {
+        val input = """
+            {title: Song}
+            {start_of_notes}
+            Paragraph one.
+
+            Paragraph two.
+
+            Paragraph three.
+            {end_of_notes}
+            {start_of_verse}
+            text
+            {end_of_verse}
+        """.trimIndent()
+        val song = ChordProParser.parse(input)
+        song.notes shouldHaveSize 3
+        song.notes[0] shouldBe "Paragraph one."
+        song.notes[1] shouldBe "Paragraph two."
+        song.notes[2] shouldBe "Paragraph three."
+    }
 }