Multiworkspace tasks could not complete due to two independent bugs:
1. task.workspaceWorktrees had no SQLite column / rowToTask mapping, so
fn_acquire_repo_worktree's updateTask write was dropped on every persist
(applyTaskPatch writes the DB-round-tripped task back to task.json). Every
later getTask returned undefined, so fn_task_done's scope verifier read {}
and blocked with "acquired no sub-repo worktrees", and isWorkspaceTask()
consumers misfired. Persist it mirroring mergeDetails (schema column + v129
migration + db-migrate + defineTaskColumn + TaskRow + rowToTask).
2. In workspace mode every task ran rooted at the shared browse-only root, and
setActiveSession registered that path keyed only by path — so a second
concurrent workspace task was rejected by the foreign-task guard
("active-session path ... is held by ..."). Give each task a task-scoped
synthetic session key (sessionRegistryPath), applied at all register and
unregister sites; the in-memory worktree Set still holds the real root.
Regression tests assert the persistence invariant across getTask/listTasks/
store-reopen and concurrent session registration across all three session
surfaces; both verified to fail without the fix.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
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