[DF2] #36: Sub-subsection indentation renders as code blocks on GitHub

[v1d0b0t]

Automated pipeline PR for #36

[v1d0b0t]

Implementation Plan

1. Inspect src/transforms/markdown.ts render paths to isolate the existing top-level subsection flow from deeper labeled descendants.
2. Add a depth/descendant-aware GitHub-safe rendering branch so only nested labeled hierarchies switch to bold paragraph blocks with exact blank-line separation.
3. Keep flat sections and top-level-subsection-only sections byte-stable, including existing inline subsection formatting from issue Formatting round 2: anchor tags visible, subsections not separated #31.
4. Verify continuation/body lines inside affected nested hierarchies stay below GitHub's four-space code-block threshold while preserving source order.
5. Run rtk test npx vitest run, rtk err npx tsc --noEmit, and rtk err npm run build, then commit/push and update the issue/PR state.

[v1d0b0t]

[adversary-review] — APPROVED

[v1d0b0t]

[adversary-review] — APPROVED