fix: make Review action list issues without auto-fixing (#167)

## Summary
- Updated the Review agent action prompt to instruct the agent to
identify and list issues rather than immediately fixing them
- The agent now presents findings as a clear list and asks the user
which ones (if any) to address

## Test plan
- [ ] Click the Review action button in a workspace with changes
- [ ] Verify the agent lists issues without auto-fixing them
- [ ] Verify the agent asks the user for input before proceeding

Author: hmans

internal/graph/agent_helpers.go

@@ -199,7 +199,9 @@ var agentActions = []agentActionDef{
 		Label:       "Review",
 		Description: "Ask for a code review",
 		PromptFunc: func(_ actionContext) string {
-			return "Ask a subagent for a thorough code review."
+			return `Review the changes in this branch. Identify any issues, concerns, or suggestions, and present them as a clear list.
+
+IMPORTANT: Do NOT fix anything automatically. Only identify and list the issues, then ask the user which ones (if any) they'd like you to address.`
 		},
 	},
 	{

internal/graph/schema.resolvers_test.go

@@ -2989,8 +2989,8 @@ func TestExecuteAgentAction(t *testing.T) {
 			t.Fatal("expected session to exist")
 		}
 		lastMsg := session.Messages[len(session.Messages)-1]
-		if lastMsg.Content != "Ask a subagent for a thorough code review." {
-			t.Fatalf("expected review prompt, got: %s", lastMsg.Content)
+		if !strings.Contains(lastMsg.Content, "Do NOT fix anything automatically") {
+			t.Fatalf("expected review prompt with no-auto-fix instruction, got: %s", lastMsg.Content)
 		}
 	})