Document new AMT_HIDE_NAMETAGS modifier for AvatarModifierArea

## Description

The new `AMT_HIDE_NAMETAGS` modifier has been added to `AvatarModifierArea` via:
- SDK PR: https://github.com/decentraland/js-sdk-toolchain/pull/1401
- Explorer PR: https://github.com/decentraland/unity-explorer/pull/8823
- Protocol PR: https://github.com/decentraland/protocol/pull/411

The creator documentation needs to be updated to include this new modifier:

1. Add `AvatarModifierType.AMT_HIDE_NAMETAGS` to the list of supported modifiers
2. Add a new section explaining the feature with a code example
3. Document interaction with other modifiers (e.g., stacking with `AMT_HIDE_AVATARS`)
4. Update the AI SDK context files
5. Update the Spanish translation

## Context

This modifier allows scene creators to hide player nametags within a defined area while keeping avatars visible — useful for stages, presentations, or scripted scenes where creators want to suppress player nametags without hiding avatars.

### Files to update

- `creator/sdk7/interactivity/player-avatar.md` (English)
- `creator-esp/sdk7/interactivity/avatar-modifiers.md` (Spanish)
- `ai-sdk-context/sdk7-complete-reference.md`
- `ai-sdk-context/sdk7-examples.mdc`

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Reported by giorgio298 via Slack
Requested by gonzalo (<@U097SSTNBUM>)

Start with creator/sdk7/interactivity/player-avatar.md and inspect how existing AvatarModifierType values and examples are documented. Update the English page, Spanish translation, and both AI SDK context files listed in the issue, covering AMT_HIDE_NAMETAGS and its interaction with other modifiers; done means all four files consistently describe the new modifier.

Written by the indexing model from the issue text.