Add READY state for human-in-the-loop verification

Top-level tasks now land in READY after successful execution instead of
going directly to COMPLETED. Subtasks (with parent_task_id) skip the gate
and remain COMPLETED. Users accept or reject via new API endpoints:

  POST /api/tasks/{id}/accept  → READY → COMPLETED
  POST /api/tasks/{id}/reject  → READY → PENDING (with rejection_comment)

- task: add StateReady, RejectionComment field, update ValidTransition
- storage: migrate rejection_comment column, add RejectTask method
- executor: route top-level vs subtask to READY vs COMPLETED
- api: /accept and /reject handlers with 409 on invalid state

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

1 files changed, 14 insertions, 0 deletions

diff --git a/internal/task/task_test.go b/internal/task/task_test.go
index a8e0a84..6498271 100644
--- a/internal/task/task_test.go
+++ b/internal/task/task_test.go
@@ -45,6 +45,7 @@ func TestValidTransition_DisallowedTransitions(t *testing.T) {
 		{"completed to queued", StateCompleted, StateQueued},
 		{"failed to completed", StateFailed, StateCompleted},
 		{"timed out to completed", StateTimedOut, StateCompleted},
+		{"ready to queued", StateReady, StateQueued},
 	}
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
@@ -55,6 +56,19 @@ func TestValidTransition_DisallowedTransitions(t *testing.T) {
 	}
 }
 
+func TestValidTransition_ReadyState(t *testing.T) {
+	valid := []struct{ from, to State }{
+		{StateRunning, StateReady},
+		{StateReady, StateCompleted},
+		{StateReady, StatePending},
+	}
+	for _, tt := range valid {
+		if !ValidTransition(tt.from, tt.to) {
+			t.Errorf("expected transition %s -> %s to be valid", tt.from, tt.to)
+		}
+	}
+}
+
 func TestDuration_UnmarshalYAML(t *testing.T) {
 	var d Duration
 	unmarshal := func(v interface{}) error {