feat: colonnes multi-colonnes (layout côte à côte style Notion)

- Architecture nested nodes: columns container → column children
- CSS seamless (pas de bordures, fin séparateur vertical entre colonnes)
- isolating: true sur les deux nœuds (curseur reste dans sa colonne)
- Commands addColumnBefore/addColumnAfter/deleteColumn
- Slash menu + drag handle + raccourci Mod+Shift+L
- i18n FR/EN complet

memento-note/components/tiptap-columns-extension.tsx

@@ -0,0 +1,159 @@
+'use client'
+
+import { Node, mergeAttributes, findParentNode } from '@tiptap/core'
+import { TextSelection } from '@tiptap/pm/state'
+import type { EditorState, Transaction } from '@tiptap/pm/state'
+import type { Node as PMNode } from '@tiptap/pm/model'
+
+export const ColumnNode = Node.create({
+  name: 'column',
+  content: 'block+',
+  isolating: true,
+  defining: true,
+
+  addAttributes() {
+    return {
+      index: {
+        default: 0,
+        parseHTML: (el) => Number(el.getAttribute('index')) || 0,
+        renderHTML: (attrs) => ({ index: attrs.index }),
+      },
+    }
+  },
+
+  parseHTML() {
+    return [{ tag: 'div[data-type="column"]' }]
+  },
+
+  renderHTML({ HTMLAttributes }) {
+    return [
+      'div',
+      mergeAttributes(HTMLAttributes, {
+        'data-type': 'column',
+        class: 'tiptap-column',
+      }),
+      0,
+    ]
+  },
+})
+
+export const ColumnsExtension = Node.create({
+  name: 'columns',
+  group: 'block',
+  content: 'column{1,}',
+  isolating: true,
+  defining: true,
+  allowGapCursor: false,
+
+  addAttributes() {
+    return {
+      cols: {
+        default: 2,
+        parseHTML: (el) => Number(el.getAttribute('cols')) || 2,
+        renderHTML: (attrs) => ({ cols: attrs.cols }),
+      },
+    }
+  },
+
+  parseHTML() {
+    return [{ tag: 'div[data-type="columns"]' }]
+  },
+
+  renderHTML({ HTMLAttributes }) {
+    return [
+      'div',
+      mergeAttributes(HTMLAttributes, {
+        'data-type': 'columns',
+        class: 'tiptap-columns',
+      }),
+      0,
+    ]
+  },
+
+  addCommands() {
+    return {
+      addColumnAfter: () => ({ state, dispatch }: { state: EditorState; dispatch?: (tr: Transaction) => void }) => {
+        return addOrDeleteCol(state, dispatch, 'addAfter')
+      },
+      addColumnBefore: () => ({ state, dispatch }: { state: EditorState; dispatch?: (tr: Transaction) => void }) => {
+        return addOrDeleteCol(state, dispatch, 'addBefore')
+      },
+      deleteColumn: () => ({ state, dispatch }: { state: EditorState; dispatch?: (tr: Transaction) => void }) => {
+        return addOrDeleteCol(state, dispatch, 'delete')
+      },
+    }
+  },
+
+  addKeyboardShortcuts() {
+    return {
+      'Mod-Shift-L': () => this.editor.commands.insertContent({
+        type: this.name,
+        attrs: { cols: 2 },
+        content: [
+          { type: 'column', attrs: { index: 0 }, content: [{ type: 'paragraph' }] },
+          { type: 'column', attrs: { index: 1 }, content: [{ type: 'paragraph' }] },
+        ],
+      }),
+    }
+  },
+})
+
+function addOrDeleteCol(state: EditorState, dispatch?: (tr: Transaction) => void, type?: 'addBefore' | 'addAfter' | 'delete'): boolean {
+  const maybeColumns = findParentNode((node: PMNode) => node.type.name === 'columns')(state.selection)
+  const maybeColumn = findParentNode((node: PMNode) => node.type.name === 'column')(state.selection)
+
+  if (!maybeColumns || !maybeColumn) return false
+
+  const cols = maybeColumns.node
+  const colIndex = maybeColumn.node.attrs.index
+  const colsJSON = cols.toJSON()
+
+  let nextIndex = colIndex
+
+  if (type === 'delete') {
+    if (colsJSON.content.length <= 1) return false
+    nextIndex = Math.max(0, colIndex - 1)
+    colsJSON.content.splice(colIndex, 1)
+  } else {
+    nextIndex = type === 'addBefore' ? colIndex : colIndex + 1
+    colsJSON.content.splice(nextIndex, 0, {
+      type: 'column',
+      attrs: { index: colIndex },
+      content: [{ type: 'paragraph' }],
+    })
+  }
+
+  colsJSON.attrs.cols = colsJSON.content.length
+  colsJSON.content.forEach((colJSON: any, index: number) => {
+    colJSON.attrs.index = index
+  })
+
+  const nextCols = PMNode.fromJSON(state.schema, colsJSON)
+
+  let nextSelectPos = maybeColumns.pos + 1
+  nextCols.content.forEach((col: PMNode, _pos: number, index: number) => {
+    if (index < nextIndex) nextSelectPos += col.nodeSize
+  })
+
+  if (dispatch) {
+    const tr = state.tr
+    tr.replaceWith(maybeColumns.pos, maybeColumns.pos + maybeColumns.node.nodeSize, nextCols)
+    tr.setSelection(TextSelection.near(tr.doc.resolve(nextSelectPos + 1)))
+    dispatch(tr)
+  }
+
+  return true
+}
+
+export function insertColumnsBlock(editor: any, columns: number = 2) {
+  const content = Array.from({ length: columns }, (_, i) => ({
+    type: 'column',
+    attrs: { index: i },
+    content: [{ type: 'paragraph' }],
+  }))
+  editor.chain().focus().insertContent({
+    type: 'columns',
+    attrs: { cols: columns },
+    content,
+  }).run()
+}