feat(docx): support cross-document paragraph cloning with source formatting

Problem

officecli add <file> <parent> --from <path> can clone a paragraph only within the same DOCX file. When an agent needs to assemble a new document from existing Word documents, the available paragraph-level dump/batch path does not carry sibling document resources such as styles, numbering, and theme definitions. As a result, copying a paragraph into a new DOCX cannot reliably match Word's Keep Source Formatting behavior.

Proposed interface

Add an explicit source-document option, or an equivalent cross-document clone operation:

officecli add target.docx /body `
  --from-file source.docx `
  --from "/body/p[12]" `
  --after "/body/p[3]"

The source document should remain read-only.

Expected behavior

For a copied Word paragraph:

• preserve paragraph properties and all child runs/direct character formatting;
• import or remap referenced custom styles and numbering definitions;
• preserve theme-dependent appearance where required;
• copy and remap media and hyperlink relationships used by the paragraph;
• remap colliding bookmark, comment, footnote, endnote, drawing, and relationship IDs;
• reuse identical target definitions where safe and handle conflicting definitions deterministically;
• produce a DOCX that passes officecli validate and opens correctly in Microsoft Word.

Motivation

This is useful for contract assembly, compliance-review summaries, report compilation, and other workflows that collect selected source paragraphs into a new Word document. Today agents can find the paragraph and clone it inside its original document, but cannot transfer it to a new document with source formatting intact.

A paragraph-first implementation would already cover the primary use case; support for tables and other block elements could follow separately.