Epic 6: Stories 6-2 (Markdown roundtrip) + 6-3 (Brainstorm PPTX + Canvas)

Story 6-2 — Markdown roundtrip export/import:
- lib/editor/markdown-export.ts: tiptapHTMLToMarkdown, markdownToHTML, looksLikeMarkdown
- lib/editor/markdown-paste-extension.ts: TipTap extension paste Markdown → blocs
- note-editor-toolbar.tsx: export .md + import .md (file picker)
- rich-text-editor.tsx: intégration MarkdownPasteExtension
- 40 tests unitaires markdown-export.test.ts

Story 6-3 — Brainstorm PPTX + Canvas:
- lib/brainstorm/export-pptx.ts: génération PPTX 5 slides (pptxgenjs)
- app/api/brainstorm/[sessionId]/export-pptx/route.ts: route POST protégée
- brainstorm-page.tsx: bouton PPTX, auto-select session, fix emoji, fix router.replace
- wave-canvas.tsx: fitTrigger recentrage, légende bas-droite

Onboarding activation wizard (Story 6-1):
- components/onboarding/: wizard multi-étapes, hints éditeur
- app/api/onboarding/: route PATCH onboarding
- prisma/migrations: champs onboarding user

Locales: 15 langues mises à jour (brainstorm, markdown, onboarding keys)
Sprint: 6-1 done, 6-2 review, 6-3 review

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

memento-note/locales/zh.json

@@ -2176,7 +2176,12 @@
       "Italiano": "意大利语",
       "Chinois": "中文",
       "Japonais": "日语"
-    }
+    },
+    "exportMarkdown": "导出为 Markdown",
+    "importMarkdown": "导入 Markdown",
+    "markdownExportSuccess": "笔记已导出为 Markdown",
+    "markdownExportError": "笔记导出失败",
+    "markdownImportSuccess": "Markdown 导入成功"
   },
   "brainstorm": {
     "title": "Waves of Thought",
@@ -2306,7 +2311,16 @@
     "ownerBadge": "Owner",
     "waveBadge": "Wave {wave}",
     "quotaGuest": "会话主持人已达到 AI 额度上限。请让对方升级套餐。",
-    "quotaHost": "您已达到此头脑风暴的 AI 额度上限。升级套餐以继续。"
+    "quotaHost": "您已达到此头脑风暴的 AI 额度上限。升级套餐以继续。",
+    "downloadPptx": "PPTX",
+    "downloadPptxDesc": "下载为 PowerPoint",
+    "pptxSuccess": "PPTX 已下载",
+    "pptxError": "PPTX 导出失败",
+    "fitToScreen": "重新居中",
+    "legendWave1": "变体",
+    "legendWave2": "类比",
+    "legendWave3": "颠覆",
+    "legendConverted": "已转换"
   },
   "usageMeter": {
     "packName": "AI Discovery Pack",
@@ -2762,5 +2776,96 @@
     "uploadError": "上传错误",
     "uploadFailed": "上传失败",
     "uploading": "上传中..."
+  },
+  "onboarding": {
+    "welcome_title": "您的AI增强记忆",
+    "welcome_subtitle": "Momento记住您忘记的事情。",
+    "welcome_cta": "开始",
+    "skip": "跳过",
+    "step_notes_title": "您的笔记",
+    "step_notes_empty": "您还没有笔记。导入您的笔记或从示例开始。",
+    "step_notes_import": "导入我的笔记",
+    "step_notes_demo": "创建5个示例笔记",
+    "step_notes_has_notes": "您已有{count}条笔记。让我们发现魔力。",
+    "step_notes_cta": "我的笔记已准备好",
+    "step_aha_title": "找到您忘记的内容",
+    "step_aha_subtitle": "提问。找到您遗忘的笔记。",
+    "step_aha_placeholder": "关于生产力的笔记...",
+    "step_aha_cta": "探索Momento",
+    "progress": "{current}/{total}",
+    "creating_demo_notes": "正在创建示例笔记...",
+    "demo_notes_ready": "已创建5个示例笔记！",
+    "badge_credits": "⚡ 剩余 {count} 积分",
+    "badge_upgrade": "升级到 Pro →",
+    "no_results": "无结果 — 请尝试其他查询。",
+    "search_credit_used": "已使用 1 次搜索",
+    "quota_exceeded": "搜索配额已用完 — 升级到 Pro。",
+    "step_aha_search_button": "搜索",
+    "step_aha_search_aria": "搜索您的笔记",
+    "step_notes_hint": "💡 这些笔记将在下一步为 AI 搜索演示提供支持。",
+    "step_features_title": "您的 AI 超能力",
+    "step_features_subtitle": "选择从哪里开始。",
+    "step_features_cta": "开始吧！",
+    "feature_search_title": "语义搜索",
+    "feature_search_desc": "按含义查找任何笔记，而不仅仅是关键词。",
+    "feature_flashcards_title": "AI 闪卡",
+    "feature_flashcards_desc": "一键从笔记生成 SRS 复习卡片。",
+    "feature_brainstorm_title": "AI 头脑风暴",
+    "feature_brainstorm_desc": "AI 驱动的协作头脑风暴会话。",
+    "feature_chat_title": "与笔记对话",
+    "feature_chat_desc": "向您的个人知识库提问。",
+    "feature_insights_title": "语义洞察",
+    "feature_insights_desc": "发现您想法之间隐藏的联系。",
+    "feature_export_title": "Markdown 导出",
+    "feature_export_desc": "以标准 Markdown 格式导入和导出笔记。",
+    "welcome_title_name": "你好 {name} 👋",
+    "import_formats": "支持格式：.md, .txt",
+    "import_error": "部分文件无法导入，请重试。",
+    "import_notes_ready": "已导入 {count} 篇笔记！",
+    "action_write_title": "写下您的第一篇真实笔记",
+    "action_write_desc": "创建笔记，开始记录您的想法。",
+    "action_flashcards_title": "生成您的第一批闪卡",
+    "action_flashcards_desc": "打开笔记，点击闪卡按钮。",
+    "action_brainstorm_title": "开始AI头脑风暴",
+    "action_brainstorm_desc": "与AI代理探索您的想法。",
+    "action_try": "试试",
+    "step_features_cta_all": "全部完成——开始吧！",
+    "action_write_where": "关闭此窗口 → 点击侧边栏\"+ 新建笔记\"",
+    "action_flashcards_where": "关闭 → 打开笔记 → 工具栏中的 🃏 按钮",
+    "action_brainstorm_where": "关闭 → 侧边栏\"Canvas\"区域",
+    "pill_resume": "✨ 继续引导",
+    "action_done": "已试用",
+    "editor_hints_title": "Editor tips",
+    "editor_hints_got_it": "Got it!",
+    "hint_slash_title": "\"/\" command — insert blocks",
+    "hint_slash_desc": "In the editor, type \"/\" to open the block menu: heading, list, code block, table, to-do list, and AI commands (Clarify, Shorten, Improve, Expand).",
+    "hint_ai_title": "Built-in AI assistant",
+    "hint_ai_desc": "Click the ✨ button in the toolbar to open the AI panel — ask questions, summarize, rewrite, or brainstorm directly in your note.",
+    "hint_version_title": "Version history",
+    "hint_version_desc": "Click the ⓘ button in the toolbar → \"Versions\" tab. Enable versioning, then save and restore snapshots of your note at any time.",
+    "hint_flashcards_title": "Generate flashcards",
+    "hint_flashcards_desc": "Click the 🎓 button in the toolbar to auto-generate flashcards from your note for spaced repetition review.",
+    "hint_links_title": "Links between notes",
+    "hint_links_desc": "Type \"[[\" in the editor to search and link to another note. Linked notes appear as backlinks at the bottom of the note.",
+    "hint_create_note_title": "Create a note",
+    "hint_create_note_desc": "Click the \"+\" button in the sidebar or press Ctrl+N to create a new note. Then start writing.",
+    "hint_flip_title": "Flip the card",
+    "hint_flip_desc": "Press Space (or click the card) to flip it and reveal the answer.",
+    "hint_rate_keys_title": "Rate with keyboard",
+    "hint_rate_keys_desc": "After flipping, press 1 (Hard), 2 (Difficult), 3 (Good) or 4 (Easy) to rate the card. The SM-2 algorithm schedules your next review automatically.",
+    "hint_generate_from_note_title": "Generate from a note",
+    "hint_generate_from_note_desc": "Open any note and click the 🎓 button in the toolbar to automatically generate flashcards from its content.",
+    "hint_brainstorm_start_title": "Start with an idea",
+    "hint_brainstorm_start_desc": "Type any concept or question in the input field and press Enter. The AI will generate a set of ideas around it.",
+    "hint_brainstorm_deepen_title": "Deepen an idea",
+    "hint_brainstorm_deepen_desc": "Click on any idea card to expand it with sub-ideas and explore it further.",
+    "hint_brainstorm_export_title": "Export your session",
+    "hint_brainstorm_export_desc": "When done, export the entire brainstorm session as a structured note saved to your notebook.",
+    "hint_insights_clusters_title": "Note clusters",
+    "hint_insights_clusters_desc": "Your notes are automatically grouped into thematic clusters. Click a cluster to explore the notes it contains.",
+    "hint_insights_bridge_title": "Bridge notes",
+    "hint_insights_bridge_desc": "Bridge notes connect multiple clusters. They are highlighted because they hold your knowledge graph together.",
+    "hint_insights_refresh_title": "Refresh clusters",
+    "hint_insights_refresh_desc": "If you've added new notes, click the refresh button to recalculate the clusters with the latest content."
   }
-}
+}