fix(agent): reduce verbose responses — focus answers on user's question only

Root cause: when planner fails (402 payment), legacy loop dumps all system
context to LLM which outputs everything. Also final response prompt was too
weak — LLM treated all observations as required output.

Changes:
- Strengthen system prompt: "answer ONLY what user asked", no tables/tutorials
  unless requested, no self-intro repeats, no "next step" suggestions
- Add compact observation summary for final response (step summaries only,
  no raw JSON blobs)
- Domain-filtered tool selection in legacy loop to prevent over-fetching
- Fix domain routing: "钱包/wallet" → account domain (not model), with
  exchange configs included for wallet context
- Widen wallet fast-path: no longer requires "claw402" keyword
- Anti-repetition instructions in planner step selector

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

agent/model_wallet_fastpath.go

@@ -8,11 +8,19 @@ import (
 
 func isModelWalletBalanceQuestion(text string) bool {
 	lower := strings.ToLower(strings.TrimSpace(text))
-	if lower == "" || !strings.Contains(lower, "claw402") {
+	if lower == "" {
 		return false
 	}
-	return containsAny(lower, []string{"余额", "balance", "usdc"}) &&
-		containsAny(lower, []string{"钱包", "wallet", "主钱包", "base"})
+	// Direct wallet address questions: "我的钱包地址", "wallet address", etc.
+	if containsAny(lower, []string{"钱包", "wallet"}) && containsAny(lower, []string{"地址", "address"}) {
+		return true
+	}
+	// Balance questions with wallet context
+	if containsAny(lower, []string{"余额", "balance", "usdc"}) &&
+		containsAny(lower, []string{"钱包", "wallet", "主钱包", "base", "claw402"}) {
+		return true
+	}
+	return false
 }
 
 func (a *Agent) handleModelWalletBalanceQuestion(storeUserID, lang, text string) (string, bool) {