POST /sessions no longer silently drops `workspace`. ThtRunner.run/json take an optional workspace; configArg() selects workspaces/<ws>.yaml when it exists under harnessDir, else falls back to default configPath. sessionNew threads workspace through. Route forwards b.workspace with an MVP note (gate/Pi side still single-workspace via symlinked config/tht.yaml). 19/19 tests pass, tsc clean. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>