fix(terminal): copy wide characters selected from either half (#7260)

Include the leading cell when a selection starts on a wide character continuation, matching the native renderer highlight. Keep continuation cells out of copied text so real spaces remain unchanged.

Co-authored-by: paseo-bot[bot] <266920839+paseo-bot[bot]@users.noreply.github.com>

packages/app/src/terminal/native-renderer/terminal-selection.test.ts

@@ -41,6 +41,48 @@ function rowWithText(
 }
 
 describe("native terminal selection", () => {
+  it.each([
+    { startCol: 1, endCol: 8, expected: "한글 문장" },
+    { startCol: 3, endCol: 8, expected: "글 문장" },
+    { startCol: 1, endCol: 1, expected: "한" },
+    { startCol: 0, endCol: 0, expected: "한" },
+    { startCol: 0, endCol: 1, expected: "한" },
+    { startCol: 4, endCol: 6, expected: " 문" },
+  ])(
+    "copies complete wide characters for selected columns $startCol through $endCol",
+    async ({ startCol, endCol, expected }) => {
+      const terminal = createNativeHeadlessTerminal({ rows: 3, cols: 30 });
+      const copied: string[] = [];
+      try {
+        await terminal.write("한글 문장");
+        const bounds = terminal.getBufferBounds();
+        const selection = createTerminalSelectionModel();
+        selection.begin({
+          coordinate: { row: bounds.cursorRow, col: endCol },
+          bounds,
+        });
+        selection.update({
+          coordinate: { row: bounds.cursorRow, col: startCol },
+          bounds,
+        });
+
+        await copyTerminalSelection({
+          terminal,
+          selection: selection.getSnapshot().range,
+          clipboard: {
+            writeText: async (text) => {
+              copied.push(text);
+            },
+          },
+        });
+
+        expect(copied).toEqual([expected]);
+      } finally {
+        terminal.dispose();
+      }
+    },
+  );
+
   it("copies Korean output without adding spaces for continuation cells", async () => {
     const terminal = createNativeHeadlessTerminal({ rows: 3, cols: 30 });
     const copied: string[] = [];

packages/app/src/terminal/native-renderer/terminal-selection.ts

@@ -324,9 +324,13 @@ export function extractTerminalSelectedText(input: TerminalSelectedTextInput): s
     const cells = window.rows[offset] ?? [];
     const startsOnThisRow = row === selection.start.row;
     const endsOnThisRow = row === selection.end.row;
-    const startCol = startsOnThisRow ? selection.start.col : 0;
+    let startCol = Math.max(0, startsOnThisRow ? selection.start.col : 0);
+    // Selecting either half highlights the whole wide character, so copy its leading cell too.
+    if (startCol > 0 && cells[startCol]?.width === 0) {
+      startCol -= 1;
+    }
     const endCol = endsOnThisRow ? selection.end.col : cells.length - 1;
-    const selectedCells = cells.slice(Math.max(0, startCol), Math.max(0, endCol) + 1);
+    const selectedCells = cells.slice(startCol, Math.max(0, endCol) + 1);
     const line = selectedCells
       .filter((cell) => cell.width !== 0)
       .map((cell) => cell.char)