Allow triple-click to select logical line (#18885)

This fixes #18877, by iteratively checking to see if a line is wrapped
and moving up or down accordingly.

**Current behavior:** When a user triple-clicks on a line that’s
visually wrapped by the terminal, only the single physical row that was
clicked gets selected.

**Expected behavior:** A triple-click like in xterm, should select the
entire logical line including all of its wrapped segments, from the true
start through its true end, regardless of where the wrap occurred.

**Why it matters:** Logical line selection is what users expect when
they’re trying to grab one command or output block in full. Limiting the
selection to just the current physical row can lead to copy/paste
mistakes and a confusing experience whenever a long line wraps.

## Validation Steps Performed
I ran the existing tests using `Invoke-OpenConsoleTests` and they were
passing and I was also able to test the build on my machine. I added a
test case as well

## PR Checklist
Closes #18877

Author: albus-droid

src/cascadia/TerminalCore/TerminalSelection.cpp

@@ -294,9 +294,21 @@ std::pair<til::point, til::point> Terminal::_ExpandSelectionAnchors(std::pair<ti
 
     const auto& buffer = _activeBuffer();
     const auto bufferSize = buffer.GetSize();
+    const auto height = buffer.GetSize().Height();
+
     switch (_multiClickSelectionMode)
     {
     case SelectionExpansion::Line:
+        // climb up to the first row that is wrapped
+        while (start.y > 0 && buffer.GetRowByOffset(start.y - 1).WasWrapForced())
+        {
+            --start.y;
+        }
+        // climb down to the last row that is wrapped
+        while (end.y + 1 < height && buffer.GetRowByOffset(end.y).WasWrapForced())
+        {
+            ++end.y;
+        }
         start = { bufferSize.Left(), start.y };
         end = { bufferSize.RightExclusive(), end.y };
         break;

src/cascadia/UnitTests_TerminalCore/SelectionTest.cpp

@@ -549,6 +549,21 @@ namespace TerminalCoreUnitTests
             ValidateLinearSelection(term, { 0, 10 }, { term.GetViewport().RightExclusive(), 10 });
         }
 
+        TEST_METHOD(TripleClick_WrappedLine)
+        {
+            Terminal term{ Terminal::TestDummyMarker{} };
+            DummyRenderer renderer{ &term };
+            term.Create({ 10, 5 }, 0, renderer);
+            term.Write(L"ABCDEFGHIJKLMNOPQRSTUVWXYZ");
+
+            // Simulate click at (x,y) = (3,1)
+            auto clickPos = til::point{ 3, 1 };
+            term.MultiClickSelection(clickPos, Terminal::SelectionExpansion::Line);
+
+            // Validate selection area
+            ValidateLinearSelection(term, { 0, 0 }, { term.GetViewport().RightExclusive(), 2 });
+        }
+
         TEST_METHOD(TripleClickDrag_Horizontal)
         {
             Terminal term{ Terminal::TestDummyMarker{} };