💡 Multi-line flex wrapping (flexWrap)

test/flex-wrap.test.ts で失敗しているテストを実行し、nm/repro/flex-wrap の diff を main と比較します。ops.ts のレイアウトグループを、src/clayterm.c:499 のデコードと vendored の clay/clay.h の設定まで追跡します。wrap、nowrap、wrap-reverse が要求された行配置を生成し、nowrap がデフォルトのままであれば完了です。

Is your feature request related to a problem?

A flex container lays every child out on a single main-axis line, so children that exceed the container's main-axis size overflow past it instead of breaking. In a row container 2 cells wide with children A (1 wide) and BC (2 wide), BC is placed at x:1 and overflows to x:3—past width:2—and the grid prints ABC on one row. There's no way to ask a container to wrap, which makes column-of-cards / tag-cloud layouts impossible without measuring and chunking children by hand on the JS side.

Describe the solution you'd like

A container set to wrap should start a new line when a child no longer fits along the main axis (accumulated child main size + gaps exceeds the container's main-axis size), stacking the lines along the cross axis. For the example above, BC should land at {x:0, y:1, width:2, height:1} and the grid should print A then BC on two rows.

open("root", {
  layout: {
    width: fixed(2),
    height: fixed(4),
    direction: "ltr",
    flexWrap: "wrap", // "nowrap" (default) | "wrap" | "wrap-reverse"
  },
});

flexWrap should mirror the CSS flex-wrap property. Default to "nowrap", support "wrap" and "wrap-reverse".

Describe alternatives you've considered

We can pre-measure children in JS, chunk them into rows by hand, and emit a column of explicit ltr rows. That falls apart the moment sizing is fit/grow (we'd be duplicating the renderer's own measurement) and it doesn't survive a resize without re-chunking.

Additional context

Failing test case on nm/repro/flex-wrap (test · diff).

A wrap field needs to thread through the wire format and the layout pass: the layout group in ops.ts, the layout decode in reduce (src/clayterm.c:499), and Clay_LayoutConfig in the vendored clay/clay.h, which is single-line today.