docs +update truncates multi-block Markdown content, only the first few blocks are persisted

Environment
lark-cli version: 1.0.76
OS: Windows 10 / Git Bash
Command: lark-cli docs +update --command append|block_insert_after|str_replace|overwrite
Description
When using docs +update to insert or append Markdown content that contains multiple top-level blocks (e.g., h4, p, h5, ul), only the first few blocks are persisted. The remaining content is silently discarded.

However, docs +create with the same Markdown content correctly preserves all blocks.

Steps to Reproduce
Create a Markdown file test.md:

Test Section

This is an introductory paragraph.

Subsection A

• List item 1
• List item 2

Subsection B

Another paragraph.

• List item 3
• List item 4
  Append it to an existing document:

lark-cli docs +update
--doc "https://your-domain.feishu.cn/wiki/XXXXXXXX"
--command append
--doc-format markdown
--content @test.md
Fetch the document and inspect the result.
Expected Behavior
All blocks should be appended:

Test Section heading
Introductory paragraph
Subsection A heading
Two list items
Subsection B heading
Another paragraph
Two list items
Actual Behavior
Only the first few blocks are persisted. For example:

Test Section

This is an introductory paragraph.

Subsection A

...

All remaining blocks are silently lost.

Additional Tests
docs +create --content @test.md → works, all blocks preserved.
Splitting content into individual blocks and appending one by one via script → still only ~6 blocks retained.
Tried XML and Markdown formats → same truncation.
Tried block_insert_after, append, str_replace, overwrite → all truncated.
Suspected Cause
docs +update may have an undocumented limit on the number of blocks per --content payload, or a bug in block enumeration when calling the doc v2 update API.

Start with the docs +update command and reproduce the issue using the provided test.md content and each update mode. Compare its behavior with docs +create and trace the doc v2 update API block enumeration; done means every Markdown block is persisted for append, block_insert_after, str_replace, and overwrite.