fix: move cursor pointer style on panel header to the clickable part

[ryanatkn]

The playground console header's toggle button has no cursor: pointer but its noninteractive wrapper div does, this moves the style to the button. The current behavior makes the non-clickable part appear clickable and the button not.

An alternative would be to just delete cursor: pointer; if that was the desired aesthetic but it would be less clear on desktop what's clickable. I think a small improvement, that also makes just deleting the line better, would be to move the .panel-header wrapper's padding to be a child concern, allowing the .panel-heading button to have height: 100% to fill its container.

I tried the padding change but the component is used in two places and slotted sibling styles are a bit tricky to get right, and I couldn't test the other place because Firefox/Chromium on Linux are erroring with SvelteKitError: Not found: /node_modules/.vite/deps/bindings_wasm_bg.wasm and in the browser CompileError: WebAssembly.instantiate(): expected magic word ..., I think related to this Vite issue - vitejs/vite#8427

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