fix: improve activity feed compatibility for visual diffs

- Remove HTML tags (<ins>, <del>) from diff output for activity feed compatibility
- Add callout block emoji transitions (e.g., ℹ️→🔴 for ::: info → ::: error)
- Use plain text with arrows (→) to show changes instead of HTML formatting

The activity feed doesn't support HTML tags properly, causing them to appear
as escaped text. This change uses plain text formatting that displays correctly.

Signed-off-by: Alexander Askin <[email protected]>

Author: LexioJ

lib/Service/DiffService.php

@@ -344,7 +344,7 @@ private function enhanceWithWordLevelDiff(array $operations, array $oldLines, ar
 					if (!empty(trim($line))) {
 						$formatted = $this->formatSpecialLine($line);
 						if ($formatted !== null) {
-							$lines[] = '✨' . $newLineNumber . ' <ins>' . $formatted . '</ins>';
+							$lines[] = '✨' . $newLineNumber . ' ' . $formatted;
 						}
 					}
 					break;
@@ -355,8 +355,7 @@ private function enhanceWithWordLevelDiff(array $operations, array $oldLines, ar
 					if (!empty(trim($line))) {
 						$formatted = $this->formatSpecialLine($line);
 						if ($formatted !== null) {
-							// Show old line number with strikethrough to indicate it's from old version
-							$lines[] = '🗑️<del>' . $oldLineNumber . '</del> <del>' . $formatted . '</del>';
+							$lines[] = '🗑️' . $oldLineNumber . ' ' . $formatted;
 						}
 					}
 					break;
@@ -421,14 +420,19 @@ private function generateWordLevelDiff(string $oldLine, string $newLine): string
 		if ($this->isCheckboxChange($oldLine, $newLine)) {
 			return $this->generateCheckboxDiff($oldLine, $newLine);
 		}
-		
+
+		// Check if this is a callout block type change
+		if ($this->isCalloutBlockChange($oldLine, $newLine)) {
+			return $this->generateCalloutBlockDiff($oldLine, $newLine);
+		}
+
 		// Split lines into words for comparison
 		$oldWords = $this->splitIntoWords($oldLine);
 		$newWords = $this->splitIntoWords($newLine);
-		
+
 		// Get word-level diff operations
 		$wordOps = $this->calculateDiff($oldWords, $newWords);
-		
+
 		// Render word-level diff
 		return $this->renderWordLevelHtml($wordOps, $oldWords, $newWords);
 	}
@@ -479,6 +483,38 @@ private function generateCheckboxDiff(string $oldLine, string $newLine): string
 		return $prefix . $oldCheckbox . '→' . $newCheckbox . $oldSuffix;
 	}
 
+	/**
+	 * Check if this is a callout block type change
+	 *
+	 * @param string $oldLine
+	 * @param string $newLine
+	 * @return bool
+	 */
+	private function isCalloutBlockChange(string $oldLine, string $newLine): bool {
+		return preg_match(self::CALLOUT_BLOCK_PATTERN, trim($oldLine)) &&
+		       preg_match(self::CALLOUT_BLOCK_PATTERN, trim($newLine));
+	}
+
+	/**
+	 * Generate diff for callout block type changes
+	 *
+	 * @param string $oldLine
+	 * @param string $newLine
+	 * @return string
+	 */
+	private function generateCalloutBlockDiff(string $oldLine, string $newLine): string {
+		preg_match(self::CALLOUT_BLOCK_PATTERN, trim($oldLine), $oldMatches);
+		preg_match(self::CALLOUT_BLOCK_PATTERN, trim($newLine), $newMatches);
+
+		$oldType = strtolower($oldMatches[1]);
+		$newType = strtolower($newMatches[1]);
+
+		$oldEmoji = self::CALLOUT_EMOJIS[$oldType] ?? 'ℹ️';
+		$newEmoji = self::CALLOUT_EMOJIS[$newType] ?? 'ℹ️';
+
+		return $oldEmoji . '→' . $newEmoji;
+	}
+
 	/**
 	 * Format special lines (code blocks, callouts, quotes) with emojis
 	 *
@@ -552,17 +588,17 @@ private function renderWordLevelHtml(array $operations, array $oldWords, array $
 			switch ($operation['type']) {
 				case 'add':
 					$word = $newWords[$operation['new_line']] ?? '';
-					// Add arrow if previous operation was a deletion
+					// Add arrow if previous operation was a deletion (showing replacement)
 					if ($lastWasDel) {
-						$html .= '→<ins>' . htmlspecialchars($word, ENT_QUOTES, 'UTF-8') . '</ins>';
+						$html .= '→' . htmlspecialchars($word, ENT_QUOTES, 'UTF-8');
 					} else {
-						$html .= '<ins>' . htmlspecialchars($word, ENT_QUOTES, 'UTF-8') . '</ins>';
+						$html .= htmlspecialchars($word, ENT_QUOTES, 'UTF-8');
 					}
 					$lastWasDel = false;
 					break;
 				case 'remove':
 					$word = $oldWords[$operation['old_line']] ?? '';
-					$html .= '<del>' . htmlspecialchars($word, ENT_QUOTES, 'UTF-8') . '</del>';
+					$html .= htmlspecialchars($word, ENT_QUOTES, 'UTF-8');
 					$lastWasDel = true;
 					break;
 				case 'keep':
@@ -572,7 +608,7 @@ private function renderWordLevelHtml(array $operations, array $oldWords, array $
 					break;
 			}
 		}
-		
+
 		return $html;
 	}
 }