feat(tasks): phase 5 — ask_operator (structured question, pause, resume)

The last backend piece: when the agent hits a decision only the operator can
make, it surfaces a structured question instead of guessing or stalling.

- ask_operator(prompt, why?, options?, context_entities?): nomos-local tool
  that records a session_questions row, moves the task to awaiting_input, emits
  question.raised, and ENDS the turn (the agent loop returns after it, so the
  agent can't barrel past its own question). The prompt becomes the assistant's
  visible message so the question also shows inline in the transcript.
- Two resume paths, both close the question + emit question.answered + return
  the task to executing:
  - Panel: POST /sessions/{id}/questions/{qid}/answer → resumes the agent in the
    background with the answer injected (reusing the continuation machinery,
    refactored continueSession → resumeSession). Returns 202; the reply lands via
    message polling.
  - Chat reply: the next chat message on a task with an open question IS the
    answer — auto-closed in handleChat; the turn itself is the resume.

Verified end-to-end: forcing a decision paused the task at awaiting_input with
the structured question (prompt/why/options/entities); a panel answer resumed
the agent (it acknowledged host:strong and continued); a plain chat reply
auto-closed a second question. Cleanup + tests green.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

cmd/nomos/tasks.go

@@ -75,6 +75,32 @@ func taskToolDefs() []toolDef {
 				"required": []string{"seq", "status"},
 			},
 		},
+		{
+			Name: "ask_operator",
+			Description: "Ask the operator a question when you hit a real decision only " +
+				"they can make — an ambiguous target, a trade-off, missing information, " +
+				"or a destructive choice not already approved. This pins a structured " +
+				"question card in the context panel (with your options and the entities " +
+				"involved) and PAUSES the task until they answer; their answer resumes " +
+				"you automatically. Do NOT use it for things you can determine yourself " +
+				"with tools — only for genuine decisions.",
+			InputSchema: map[string]any{
+				"type": "object",
+				"properties": map[string]any{
+					"prompt": map[string]any{"type": "string", "description": "The question, stated plainly."},
+					"why":    map[string]any{"type": "string", "description": "Why you're asking / what's at stake."},
+					"options": map[string]any{
+						"type": "array", "items": map[string]any{"type": "string"},
+						"description": "The choices, if it's a pick-one decision.",
+					},
+					"context_entities": map[string]any{
+						"type": "array", "items": map[string]any{"type": "string"},
+						"description": "Entity slugs relevant to the decision (shown as chips).",
+					},
+				},
+				"required": []string{"prompt"},
+			},
+		},
 		{
 			Name: "complete_task",
 			Description: "Mark the current task finished. Call this once the goal is " +
@@ -103,7 +129,7 @@ func taskToolDefs() []toolDef {
 
 func isTaskTool(name string) bool {
 	switch name {
-	case "set_goal", "propose_plan", "update_plan_step", "complete_task":
+	case "set_goal", "propose_plan", "update_plan_step", "ask_operator", "complete_task":
 		return true
 	default:
 		return false
@@ -122,6 +148,21 @@ func toInt(v any) int {
 	}
 }
 
+// toStringSlice coerces a JSON tool-arg array to a non-empty []string.
+func toStringSlice(v any) []string {
+	arr, ok := v.([]any)
+	if !ok {
+		return nil
+	}
+	out := make([]string, 0, len(arr))
+	for _, e := range arr {
+		if s, ok := e.(string); ok && strings.TrimSpace(s) != "" {
+			out = append(out, s)
+		}
+	}
+	return out
+}
+
 // handleTaskTool executes a nomos-local task tool. Returns (result, true) if it
 // handled the call, or (nil, false) if name is not a local task tool (so the
 // caller forwards it to the MCP client).
@@ -174,6 +215,27 @@ func (a *agent) handleTaskTool(ctx context.Context, sessionID, name string, args
 		}
 		return fmt.Sprintf("Step %d → %s", seq, status), true
 
+	case "ask_operator":
+		prompt, _ := args["prompt"].(string)
+		if strings.TrimSpace(prompt) == "" {
+			return "error: ask_operator needs a prompt", true
+		}
+		qctx := map[string]any{}
+		if why, _ := args["why"].(string); strings.TrimSpace(why) != "" {
+			qctx["why"] = why
+		}
+		if opts := toStringSlice(args["options"]); len(opts) > 0 {
+			qctx["options"] = opts
+		}
+		if ents := toStringSlice(args["context_entities"]); len(ents) > 0 {
+			qctx["entities"] = ents
+		}
+		if _, err := a.store.askOperator(ctx, sessionID, prompt, qctx); err != nil {
+			return fmt.Sprintf("error posting question: %v", err), true
+		}
+		return "Question posted to the operator; the task is paused until they answer. " +
+			"Do not continue or call more tools — end your turn now and wait for their answer.", true
+
 	case "complete_task":
 		outcome, _ := args["outcome"].(string)
 		summary, _ := args["summary"].(string)