fix(db): make task row state authoritative

src/main/database/runs.ts

@@ -207,11 +207,6 @@ export function buildRunMethods(
           getDb()
             .prepare("UPDATE tasks SET checkout_run_id = NULL, execution_locked_at = NULL, updated_at = ? WHERE id = ? AND checkout_run_id = ?")
             .run(ts, run.taskId, input.runId);
-          // B2 Phase 1 step 3/5 — dual-write: release the shadow lease
-          // for this run at the same instant the legacy lock is cleared.
-          getDb()
-            .prepare("DELETE FROM task_leases WHERE task_id = ? AND run_id = ?")
-            .run(run.taskId, input.runId);
           if (runNeverStarted) {
             // Roll the task back to `todo` when no *other* live run claims
             // it. Invariant: `task.status = 'in_progress'` ⇒ a queued or
@@ -223,7 +218,6 @@ export function buildRunMethods(
             // NOT EXISTS clause is the canonical "no live owner" check.
             getDb()
               .prepare(
-                // eslint-disable-next-line no-restricted-syntax -- B2 Phase 1 grandfathered: finishRun's "runNeverStarted" rollback; trigger mirrors status→phase, shadow lease already dropped above
                 `UPDATE tasks
                  SET status = 'todo',
                      checkout_run_id = NULL,
@@ -276,11 +270,6 @@ export function buildRunMethods(
         getDb()
           .prepare("UPDATE tasks SET checkout_run_id = NULL, execution_locked_at = NULL, updated_at = ? WHERE id = ? AND checkout_run_id = ?")
           .run(ts, taskId, runId);
-        // B2 Phase 1 step 3/5 — dual-write: drop the shadow lease when
-        // the legacy cancellation clears checkout_run_id.
-        getDb()
-          .prepare("DELETE FROM task_leases WHERE task_id = ? AND run_id = ?")
-          .run(taskId, runId);
       }
       if (workspaceId) {
         getDb()