feat(console): JSON indent guides on result lines

Draw faint vertical guides per 2-space nesting level on result (non-channel) lines, so
nested RPC JSON is easier to read. Draw-only in the per-line loop (like the channel bar),
so it doesn't touch the text layout or selection.

Note: collapsible JSON nodes were intentionally deferred — folding entangles with the
wrap cache / filter / selection line indices and warrants a runtime-verified pass.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/ui/windows/console_tab.cpp

@@ -831,6 +831,21 @@ void ConsoleTab::renderOutput()
             }
         }
 
+        // JSON indent guides — faint vertical lines per 2-space nesting level, on result
+        // (non-channel) lines only. Draw-only, like the channel bar.
+        if (line.channel == CH_NONE) {
+            size_t leading = 0;
+            while (leading < line.text.size() && line.text[leading] == ' ') ++leading;
+            if (leading >= 2) {
+                float spaceW = font->CalcTextSizeA(fontSize, FLT_MAX, 0.0f, " ").x;
+                for (size_t c = 2; c < leading; c += 2) {
+                    float gx = lineOrigin.x + static_cast<float>(c) * spaceW;
+                    dl->AddLine(ImVec2(gx, lineOrigin.y), ImVec2(gx, lineOrigin.y + totalH),
+                                IM_COL32(255, 255, 255, 20), 1.0f);
+                }
+            }
+        }
+
         // Determine byte-level selection range for this line
         int selByteStart = 0, selByteEnd = 0;
         bool lineSelected = false;