Add an inline spoiler (Telegram/Discord-style hidden text): a TipTap mark
`spoiler` rendered as <span data-spoiler="true" class="spoiler">, blurred via
CSS and revealed on click (UI-only is-revealed class, never persisted).
- packages/editor-ext: the Spoiler mark (inclusive:false, set/toggle/unset
commands, ||text|| input rule), exported; a lossless turndown rule emitting
raw inline HTML; round-trip test.
- apps/client: SpoilerView mark-view (ReactMarkViewRenderer, Link pattern),
registration in extensions, bubble-menu toggle button (editable only), CSS
(blur + @media print reveal), en/ru i18n.
- apps/server: register Spoiler in collaboration.util tiptapExtensions so the
mark survives HTML<->JSON export/index/import/Yjs; a test proving the public
share keeps the spoiler (it isn't stripped with comments).
No keyboard shortcut: the proposed Mod-Shift-s collides with Strike (and
Mod-Shift-h with Highlight); the ||text|| input rule + the bubble-menu button
cover ergonomics.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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