feat: editor improvements and architectural grid prototype

Multiple feature additions and improvements across the application:

- NextGen Editor: drag handles, smart paste, block actions
- Structured views: Kanban and table layouts for notes
- Architectural Grid: new brainstorming/agent interface prototype
- Flashcards: SM-2 revision algorithm with AI generation
- MCP server: robustness improvements
- Graph/PDF chat: fix click propagation and copy behavior
- Various UI/UX enhancements and bug fixes

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

memento-note/lib/editor/parse-block-reference.ts

@@ -0,0 +1,67 @@
+export type ParsedBlockReference = {
+  sourceNoteId: string
+  blockId: string
+  raw: string
+}
+
+export type StoredBlockReference = ParsedBlockReference & {
+  blockContent?: string
+  sourceNoteTitle?: string
+}
+
+export const LAST_BLOCK_REF_SESSION_KEY = 'memento:lastBlockRef'
+
+/** Référence bloc copiée via « Copier la référence » : /home?openNote=…#block-… */
+export function parseBlockReferenceFromText(text: string): ParsedBlockReference | null {
+  const trimmed = text.trim()
+  if (!trimmed || trimmed.includes('\n')) return null
+
+  const match = trimmed.match(/openNote=([^&#\s]+)(?:[^#]*?)#block-([a-zA-Z0-9_-]+)/i)
+  if (!match) return null
+
+  try {
+    return {
+      sourceNoteId: decodeURIComponent(match[1]),
+      blockId: match[2],
+      raw: trimmed,
+    }
+  } catch {
+    return null
+  }
+}
+
+export function rememberBlockReference(
+  raw: string,
+  extras?: { blockContent?: string; sourceNoteTitle?: string },
+) {
+  if (typeof sessionStorage === 'undefined') return
+  const parsed = parseBlockReferenceFromText(raw)
+  if (!parsed) return
+  const payload: StoredBlockReference = {
+    ...parsed,
+    ...(extras?.blockContent ? { blockContent: extras.blockContent } : {}),
+    ...(extras?.sourceNoteTitle ? { sourceNoteTitle: extras.sourceNoteTitle } : {}),
+  }
+  try {
+    sessionStorage.setItem(LAST_BLOCK_REF_SESSION_KEY, JSON.stringify(payload))
+  } catch {
+    // quota / private mode
+  }
+}
+
+export function recallLastBlockReference(): StoredBlockReference | null {
+  if (typeof sessionStorage === 'undefined') return null
+  try {
+    const stored = sessionStorage.getItem(LAST_BLOCK_REF_SESSION_KEY)
+    if (!stored) return null
+    if (stored.startsWith('{')) {
+      const payload = JSON.parse(stored) as StoredBlockReference
+      if (payload?.sourceNoteId && payload?.blockId && payload?.raw) return payload
+      return null
+    }
+    const parsed = parseBlockReferenceFromText(stored)
+    return parsed ?? null
+  } catch {
+    return null
+  }
+}