- research_control pause/resume now validate the loop state before touching
the tree, so pausing a stopped loop can no longer leave the tree 'paused'
while the loop is not (spawn would fail until a restart).
- read_artifact confinement resolves symlinks (realpath) before checking the
project boundary, preventing symlink-based file leaks.
- Adds confinement tests (42 tests passing, tsc clean).
