Implements draft-fossil-submanifests-00 sections 5.1 through 5.6: a stack walk over S runs with the section's depth bound, cycle check, strict ascent and first-filename identity, resolving sub-manifests through the existing baseline resolver. A tree that fails any check fails whole, so a partial enumeration is never presented as a file set.

The walk sits in a pre-pass at the facade, leaving enumerate, lookup and their call sites untouched as section 9.3 requires. R-card verification runs over the walked enumeration.

Step 5's cursor advance follows the erratum submanifests-00-s5.1-step5-cursor-advance: as published, step 5 omitted it, and no tree carrying an interior node could be walked. check-in: d1f955aaf3 user: dmestas tags: sub-manifest