Revert strict dep check in find_dep_compile_layers
The strict Error-on-missing-deps approach broke all doc builds
because many deps genuinely have no documentable libs and no doc
node. OCurrent's DAG ordering already ensures deps complete before
dependents, so disk checks for dep compile layers are sufficient.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>