feat(console): collapsible JSON in command output

Add fold/unfold of JSON objects and arrays in console command results, built on
the refactored channel + model foundation.

- ComputeConsoleFoldSpans() (console_input_model): pure brace/bracket matcher
  over a block of pretty-printed JSON lines; each opener line gets the offset to
  its matching closer at the same indentation (empty/one-line blocks are not
  foldable). Unit tested (nested objects, arrays, empty blocks, non-JSON, and a
  string value that merely contains a brace).
- ConsoleModelLine gains foldSpan (relative, so it survives front-eviction by the
  line cap) + a collapsed flag; ingest() carries the span and toggleCollapsed()
  flips openers (main thread). addFormattedResult computes the block's spans and
  ingests them atomically.
- computeVisibleLines() skips a collapsed block's interior (opener stays, its
  foldSpan lines through the closer are hidden); folding is bypassed while a
  filter is active so every match stays reachable.
- drawVisibleLines() draws a fold triangle in the free left gutter of opener
  lines (result/JSON channels carry no accent bar there), toggled by a click in
  the gutter cell, and appends a dim " ... }" / " ... ]" summary on collapsed
  openers.

Full-node + lite build clean; ctest green (incl. fold-span + model-fold tests);
source hygiene clean.

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

src/ui/windows/console_input_model.h

@@ -50,5 +50,12 @@ ConsoleRpcCall BuildConsoleRpcCall(const std::string& command);
 std::vector<ConsoleResultLine> FormatConsoleRpcResultLines(const std::string& result,
                                                            bool isError);
 
+// For a block of pretty-printed JSON lines, return a per-line fold span: for a line that
+// opens a collapsible block (its last non-space char is '{' or '[') the value is the offset
+// to its matching closing-bracket line at the same indentation; 0 for every other line and
+// for empty/one-line blocks not worth folding (span < 2). Pure; used to drive console
+// JSON folding.
+std::vector<int> ComputeConsoleFoldSpans(const std::vector<std::string>& lines);
+
 } // namespace ui
 } // namespace dragonx