Keep terminal CJK text unchanged after returning to a workspace (#6452)

* fix(app): restore terminal surface after tab hide so CJK cells redraw

Retained panels use display:none. Coming back remasured without treating
that as a surface restore, so Hangul kept 2-cell slots while glyphs painted
at ~1 cell (extra gap). Reload WebGL if the context was lost and force a
refresh when the host grows from zero.

Closes #3434

* fix(server): keep wide-char continuation cells out of terminal snapshots

Wide chars (CJK) occupy two xterm cells, and the second cell reports no
chars. The snapshot capture collapsed that empty continuation to " ", so
every restored Hangul syllable took three columns instead of two. The
injected space was real: selecting and copying the restored row carried
it into the clipboard.

Capture the continuation as "" and have renderTerminalSnapshotToAnsi
skip it. No schema change; snapshots from older daemons still replay
verbatim.

* fix(app): restore retained terminals on presentation

Co-authored-by: seob717 <dev.seob717@gmail.com>

* fix(terminal): limit restoration changes to confirmed CJK corruption

Keep the independently reproduced snapshot fix. Surface recovery behavior remains unverified and belongs with the broader viewport report. Dispose the replay terminal after the regression test.

---------

Co-authored-by: Jason <mildreins@gmail.com>
Co-authored-by: seob717 <dev.seob717@gmail.com>
Co-authored-by: liujin0506 <liujin0506@qq.com>
Co-authored-by: paseo-bot[bot] <266920839+paseo-bot[bot]@users.noreply.github.com>

packages/protocol/src/terminal-snapshot.test.ts

@@ -47,3 +47,33 @@ describe("renderTerminalSnapshotToAnsi", () => {
     expect(ansi).toContain("ABCDEFGHIJ\r\nKLMNOP");
   });
 });
+
+describe("renderTerminalSnapshotToAnsi wide chars", () => {
+  it("skips wide-char continuation cells so the glyph keeps its two columns", () => {
+    // The daemon captures "통" as the glyph followed by an empty continuation
+    // cell. Emitting anything for that cell pushes the rest of the row right.
+    const state: TerminalState = {
+      rows: 1,
+      cols: 10,
+      scrollback: [],
+      grid: [[{ char: "통" }, { char: "" }, { char: "합" }, { char: "" }, { char: "!" }]],
+      cursor: { row: 0, col: 5 },
+    };
+
+    expect(renderTerminalSnapshotToAnsi(state)).toContain("통합!");
+  });
+
+  it("replays snapshots from an old daemon verbatim, including its continuation spaces", () => {
+    // Old daemons already collapsed the continuation to " ". The serializer
+    // cannot tell that apart from a real space, so it must not guess.
+    const state: TerminalState = {
+      rows: 1,
+      cols: 10,
+      scrollback: [],
+      grid: [cells("통 합 !")],
+      cursor: { row: 0, col: 6 },
+    };
+
+    expect(renderTerminalSnapshotToAnsi(state)).toContain("통 합 !");
+  });
+});

packages/protocol/src/terminal-snapshot.ts

@@ -87,6 +87,12 @@ function renderTerminalRow(row: TerminalCell[], padToCols?: number): string {
 
   for (let index = 0; index < length; index += 1) {
     const cell = row[index] ?? { char: " " };
+    // An empty char marks a wide-char continuation cell. The glyph in the
+    // previous cell already advances the cursor two columns, so emitting
+    // anything here would shift the rest of the row one column right.
+    if (cell.char === "") {
+      continue;
+    }
     const nextStyle = getTerminalStyle(cell);
     if (!terminalStylesEqual(previousStyle, nextStyle)) {
       output.push(styleToAnsi(nextStyle));