docs: separate design reference queue

- 将不直接执行的 process-reference 文档迁入各域 reference 目录

- 更新 design/README、AGENTS 和总序文档，固定 process/draft/reference/done 目录语义

- 修正活跃文档中指向旧 process 位置的参考链接

验证：git diff --check；codegraph sync .

design/06-mindmap/process/6-mindmap-kernel-phase6-projection-editor-v1.md

@@ -11,7 +11,7 @@
 > - `/mnt/Data1T/mnote/design/01-05-current-priority-overview.md`
 > - `/mnt/Data1T/mnote/design/01-tree-first-graph-kernel/process/1-tree-first-graph-kernel-v1.md`
 > - `/mnt/Data1T/mnote/design/03-rust-web/process/3-rust-web-long-term-architecture-v1.md`
-> - `/mnt/Data1T/mnote/design/05-editor-mainline/process/5-5-page-aggregate-single-truth-alignment-v1.md`
+> - `/mnt/Data1T/mnote/design/05-editor-mainline/reference/5-5-page-aggregate-single-truth-alignment-v1.md`
 >
 > 参考实现：
 > - `/mnt/Data1T/mnote/design/05-editor-mainline/reference-code/lx-doc/mind-map`