fix: tab-to-space conversion in code blocks (18 en pages affected)

[jp-knj]

Problem

Tabs in code blocks are converted to spaces, changing the original source code indentation.

Affected: ~18 en pages × 14 locales ≈ 252 pages total

Example

markflow: "\n  name: string,\n  price: number,"
baseline: "\n\tname: string,\n\tprice: number,"

Sample files: en/guides/client-side-scripts, en/guides/cms/buttercms, en/guides/cms/caisy

Root Cause

JSX normalize reindent_line logic or Rust renderer converting tabs to spaces inside code blocks.