Touch Controls: Default Button Set — creator docs update

## **⚠️ Problem:**
`creator/sdk7/interactivity/touch-screen-controls.md` documents an all-8 default gamepad. #2708 ships JUMP + POINTER + E on, F + 1–4 off until the scene opts in — the page contradicts the client on ship, and creators write `hide` calls for buttons already hidden.

## **🏁 Scope:**
Rewrite the default-visibility contract on that page: per-action default table, opt-in rule, new example, reshot figures. Layout mechanics from #2518 unchanged — the priority stack section stays as is. Ships as a PR to `decentraland/docs`, no client code.

## Dependency
Blocked by #2708. Write against shipped client behavior, not the spec.

## **📝 Deliverables:**
- [ ] Default table — JUMP / POINTER / E shown, F / 1–4 hidden
- [ ] Opt-in rule — `touchInputs` entry `hide: false`, or `PointerEvents` on the action
- [ ] Intro hint — drop "nothing hidden"
- [ ] "Leave the stack alone" row — 3 visible, not 8
- [ ] `touchInputs` property — "not listed = shown" → per-action default
- [ ] `hide` field — "Default is `false` (shown)" → per-action default
- [ ] Reflow hint — 1–4 are opt-in, not behind the "+"
- [ ] `showAll()` row — restate after SDK call (see Notes)
- [ ] Example — hiding 1–4 is now a no-op, replace with an opt-in example
- [ ] Reshoot `touch-controls-default.jpg` + `control-ordering.jpg`
- [ ] `mainAction` on a hidden-by-default action promotes **and** shows it
- [ ] PR merged in `decentraland/docs`

## Notes
`hide(actions)` has no `show(actions)` counterpart. `showAll()` = "clears the button hide list", which no longer surfaces 1–4 once defaults invert. SDK team: re-spec `showAll()` to show all 8, or add `show(actions)`. Blocks the helpers-table deliverable.

## **🔗 References:**
- [decentraland/godot-explorer#2708](https://github.com/decentraland/godot-explorer/issues/2708) — blocker; the agreed default set and client implementation this documents
- [decentraland/godot-explorer#2518](https://github.com/decentraland/godot-explorer/issues/2518) — priority stack, cascade, `mainAction`, "+" overflow; unchanged, page section stays
- [creator/sdk7/interactivity/touch-screen-controls.md](https://github.com/decentraland/docs/blob/main/creator/sdk7/interactivity/touch-screen-controls.md) — page to update
- [decentraland/docs#193](https://github.com/decentraland/docs/issues/193) — original filing, closed in favor of this issue