fix(kanban): reset failure counters on unblock_task

When a task is manually unblocked (blocked → ready/todo), the
consecutive_failures counter and last_failure_error were left intact.
The next failure would immediately re-trip the circuit breaker because
the counter was still at or above the failure limit.

Reset both fields on unblock so the task gets a fresh retry budget.

Includes a regression test that verifies counters are zeroed.

hermes_cli/kanban_db.py

@@ -2718,7 +2718,8 @@ def unblock_task(conn: sqlite3.Connection, task_id: str) -> bool:
         ).fetchone()
         new_status = "todo" if undone_parents else "ready"
         cur = conn.execute(
-            "UPDATE tasks SET status = ?, current_run_id = NULL "
+            "UPDATE tasks SET status = ?, current_run_id = NULL, "
+            "consecutive_failures = 0, last_failure_error = NULL "
             "WHERE id = ? AND status = 'blocked'",
             (new_status, task_id),
         )

tests/hermes_cli/test_kanban_db.py

@@ -406,6 +406,26 @@ def test_block_then_unblock(kanban_home):
         assert kb.get_task(conn, t).status == "ready"
 
 
+def test_unblock_resets_failure_counters(kanban_home):
+    """unblock_task must reset consecutive_failures and last_failure_error."""
+    with kb.connect() as conn:
+        t = kb.create_task(conn, title="x", assignee="a")
+        kb.claim_task(conn, t)
+        assert kb.block_task(conn, t, reason="need input")
+        # Simulate accumulated failures from the circuit breaker
+        conn.execute(
+            "UPDATE tasks SET consecutive_failures = 5, "
+            "last_failure_error = 'test error' WHERE id = ?",
+            (t,),
+        )
+        conn.commit()
+        assert kb.unblock_task(conn, t)
+        task = kb.get_task(conn, t)
+        assert task.status == "ready"
+        assert task.consecutive_failures == 0
+        assert task.last_failure_error is None
+
+
 # ---------------------------------------------------------------------------
 # Parent-completion invariant at the claim gate (RCA t_a6acd07d)
 # ---------------------------------------------------------------------------