fix(agent,claw402): harden agent runtime and strip max_tokens for thinking models

- Fix Stop() race condition using sync.Once
- Add ensureHistory() to prevent nil panic in planner/dispatcher
- Add bounds check on trader ID slicing
- Log saveExecutionState and clearSetupState errors instead of discarding
- Remove always-true modelID condition in onboard setup
- Add Chinese setup keywords and expand model name aliases
- Strip max_tokens from claw402 requests to avoid thinking-model budget exhaustion
- Hide Agent nav tab (Beta) pending merge to main
- Sync tests with code changes

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

agent/skill_dispatcher.go

@@ -661,9 +661,7 @@ func (a *Agent) tryHardSkill(ctx context.Context, storeUserID string, userID int
 }
 
 func (a *Agent) recordSkillInteraction(userID int64, userText, answer string) {
-	if a.history == nil {
-		a.history = newChatHistory(100)
-	}
+	a.ensureHistory()
 	a.history.Add(userID, "user", userText)
 	a.history.Add(userID, "assistant", answer)
 }