Feature: /spoiler slash command

[mjkatgithub]

Planning

• Milestone: Backlog (unassigned)
• Priority: P2
• Size: S
• Estimate: 1 SP

Goal

/spoiler <message> slash command — send message body as spoiler
(Element parity).

Scope

• Register /spoiler on framework (Feature: Slash-command framework in composer #110)
• Send HTML message with data-mx-spoiler wrapper (Element approach)
• i18n EN/DE description: "Send the given message as a spoiler"
• Unit test: command output shape matches timeline renderer (Feature: Timeline spoiler rendering (data-mx-spoiler) #112)

Reference

• Element SlashCommands.tsx → command: "spoiler"

Branch

feature/slash-command-spoiler

Acceptance Criteria

• /spoiler streng geheim sends masked message; reveal works (Feature: Timeline spoiler rendering (data-mx-spoiler) #112).
• Autocomplete shows /spoiler <message> with description.
• Other clients (Element) display spoiler correctly.

Test Checklist

• Unit: handler output / formatted_body structure.
• Manual: send from Decentra, verify in Element.

Blocked by

• Feature: Slash-command framework in composer #110 — slash-command framework
• Feature: Timeline spoiler rendering (data-mx-spoiler) #112 — timeline spoiler rendering

Epic

Sub-issue of #109.