mand v29a source patch

This is the first post-v28 development patch. Numeric image-processing conditions remain frozen, while tissue multicoat QC intentionally uses the supplied src.r lineage through an isolated adapter.

Important

• Do not modify the frozen v28 release.
• Keep the existing dependency files in mand_patch/R; this patch is layered on top of them.
• The generated multicoat PNG filenames now use the actual case_id; this is an intentional v29a path change.
• Numeric NIfTI outputs should match v28. QC PNG hashes are not expected to match.
• Copy R/*.R into mand_patch/R, rebuild/load the package, then run scripts/run_v29a_pilot6.R.