Why: the pin-documents flow exposed guard divergence — precheck counted
submodule drift while task-start checked porcelain only, letting a task
start despite a BUSY verdict; and PR#8 overcorrected by treating
uninitialized (-) submodules as BUSY when they only block builds, not
writes.
Evidence: bash -n clean; precheck on this checkout prints tree line with
drift/uninit split and READY verdict; negative path exercised by the
real divergence that started this task.
Impact: precheck warns on uninitialized, BUSY only on +/U; task-start now
refuses on porcelain dirt and +/U drift, matching precheck.
Refs: PR#8; policy/tool-adaptation-matrix.md A1
weichen
7c9c1e7b22