gui: extend double-click pair selection to quotes

selectBracketPair now also handles '' "" `` quote pairs. Since a
quote char opens and closes with the same glyph, a quote to the right
of the cursor scans forward for its match, and a quote to the left
scans backward.

kde/gui/ChatBlockDelegate.qml

@@ -395,6 +395,26 @@ Column {
         }
     }
 
+    function isQuote(ch) {
+        return ch === "'" || ch === '"' || ch === '`'
+    }
+
+    // Scan forward for the next occurrence of a quote char
+    function findQuoteForward(text, startPos, quote) {
+        for (var pos = startPos; pos < text.length; pos++) {
+            if (text.charAt(pos) === quote) return pos
+        }
+        return -1
+    }
+
+    // Scan backward for the previous occurrence of a quote char
+    function findQuoteBackward(text, startPos, quote) {
+        for (var pos = startPos; pos >= 0; pos--) {
+            if (text.charAt(pos) === quote) return pos
+        }
+        return -1
+    }
+
     // Find matching closer, handling nesting
     function findCloser(text, startPos, opener, closer) {
         var depth = 1
@@ -475,6 +495,20 @@ Column {
                 innerStart = cursorPos
                 innerEnd = closerPos
             }
+        } else if (isQuote(rightCh)) {
+            // Quote to right: treat as opener, find next matching quote forward
+            var qClose = findQuoteForward(text, cursorPos + 1, rightCh)
+            if (qClose >= 0) {
+                innerStart = cursorPos + 1
+                innerEnd = qClose
+            }
+        } else if (isQuote(leftCh)) {
+            // Quote to left: treat as closer, find previous matching quote backward
+            var qOpen = findQuoteBackward(text, cursorPos - 2, leftCh)
+            if (qOpen >= 0) {
+                innerStart = qOpen + 1
+                innerEnd = cursorPos - 1
+            }
         }
         
         if (innerStart >= 0 && innerEnd >= innerStart) {