[BUG] /stats Ctrl+S screenshot copy always fails on WSL2 — platform string is "wsl", the xclip branch added in #54695 only matches "linux"

### Summary

Pressing Ctrl+S on the `/stats` (or `/usage`) screen under WSL2 always shows `copy failed` in the footer. Nothing reaches the clipboard.

This is the WSL half of #54695 (`/usage` Ctrl+S silently fails to copy stats screenshot on Linux/X11, fixed 2026-05-05). That fix added an `xclip` branch keyed on the platform string `"linux"`. On WSL the platform string is `"wsl"`, so the branch never runs and the function falls through to its "unsupported platform" return.

It is the same shape as #82909 (clipboard paste on WSL only tries `powershell.exe`, Linux fallback unreachable): a platform-string branch that treats `wsl` and `linux` as disjoint when the Linux path works perfectly well on WSL2 + WSLg.

### Root cause

In `2.1.241` the screenshot-to-clipboard helper branches on `zt()`:

```js
async function KkA(e){
let t = zt();
if (t === "macos") { /* osascript */ }
if (t === "linux") { if (await YkA("xclip", ["-selection","clipboard","-t","image/png","-i", e]) === 0) return {success:true, …};
return {success:false, message:"Failed to copy to clipboard. Please install xclip: sudo apt install xclip"} }
if (t === "windows") { /* powershell Clipboard::SetImage */ }
return { success:false, message:`Screenshot to clipboard is not supported on ${t}` } // <-- WSL lands here
}
```

and `getPlatform()` classifies WSL as its own platform, never as `linux`:

```js
if (env.WSL_DISTRO_NAME || env.WSL_INTEROP) this.platform = "wsl";
else { let e = this.kernelString(); this.platform = (e !== undefined && v4o(e)) ? "wsl" : "linux" }
```

So on WSL `KkA` returns `success:false` with `"Screenshot to clipboard is not supported on wsl"`. The caller discards the message and renders only the two-word footer:

```js
n(s.success ? "copied!" : "copy failed")
```

which is why the reason is invisible to the user.

Note the codebase already has the wsl→linux collapse elsewhere — `NVo()` does `let t = e === "wsl" && !$rb() ? "linux" : e` — it just isn't applied on this path.

### Repro

1. WSL2 (WSLg available), `xclip` installed and working.
2. `claude` → `/stats` → Ctrl+S
3. Footer shows `copy failed`.
4. `xclip -selection clipboard -t TARGETS -o` — no `image/png` target; clipboard unchanged.

### Expected

Same as on native Linux: the PNG lands on the clipboard via `xclip` (WSLg bridges the X11 clipboard to the Windows clipboard, so it pastes into Windows apps too).

### Evidence that the Linux path itself works on WSL

Everything upstream of the platform check succeeds; only the branch selection is wrong.

- `xclip` is present (`/usr/bin/xclip`, 0.13) and round-trips a PNG:
```
$ xclip -selection clipboard -t image/png -i /tmp/t.png ; echo $?
0
$ xclip -selection clipboard -t TARGETS -o
TARGETS
image/png
```
- Replicating `YkA`'s exact spawn options (`{cwd: undefined, detached: true, stdio: "ignore", windowsHide: true}`, 5 s kill timer) returns `exit 0` in 4 ms.
- The render/write step runs fine: `$CLAUDE_CODE_TMPDIR/screenshots/` is created and its mtime bumps on every Ctrl+S (the PNG is written, then `unlink`ed in the `finally`). So the failure is strictly the platform branch, not `ansiToPng` and not the temp path.

### Suggested fix

Treat `wsl` like `linux` on this path, e.g. `if (t === "linux" || t === "wsl")`, or reuse the existing `NVo()`-style collapse before the branch. Verified locally: binary-patching that one comparison to `t !== "macos"` makes Ctrl+S copy the screenshot correctly on WSL2.

A second, independent nit: the "unsupported platform" and "install xclip" messages are both swallowed by the `copied!`/`copy failed` footer, so every distinct failure mode presents identically. Surfacing `s.message` on failure would have made this self-diagnosing.

### Environment

- Claude Code: **2.1.241**
- WSL2 on Windows 11, kernel **6.18.33.2-microsoft-standard-WSL2**
- Distro: **Ubuntu 24.04.3 LTS**
- `WSL_DISTRO_NAME=Ubuntu`, `WSL_INTEROP=/run/WSL/_interop`
- WSLg: `DISPLAY=:0`, `WAYLAND_DISPLAY=wayland-0` (`XDG_SESSION_TYPE` unset)
- `xclip` 0.13 installed and functional; `wl-clipboard` not installed
- `TERM=xterm-256color`

### Related

- #54695 — same bug on Linux/X11, fixed by adding the `linux` branch this report says WSL misses
- #82909 — clipboard **paste** on WSL only tries `powershell.exe`; same class of platform-branch gap

Start at the screenshot-to-clipboard helper KkA and the zt() platform classification described in the issue, then reproduce the Ctrl+S flow on WSL2 with xclip installed. Confirm that the WSL path reaches the working Linux clipboard behavior and that /stats or /usage reports copied successfully without regressing native Linux or other platforms.

Escrito por el modelo de indexación a partir del texto del issue.