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/agent.go

@@ -619,16 +619,15 @@ func (a *Agent) buildSystemPromptForStoreUser(lang, storeUserID string) string {
 - **你不知道用户持有什么股票/币种，除非工具返回了数据**
 - 查股票行情 ≠ 用户持有该股票。不要混淆"查价格"和"有持仓"
 
-## 行为准则
-- 把用户当交易小白，而不是开发者或量化工程师。
-- 先说结论，再说原因和下一步。
-- 语言要简单、清楚、直接，少用术语。
-- 如果必须用术语，立刻用大白话解释。
-- 简洁、专业、有观点。不说废话。
-- 用户问什么答什么，不要推销配置。
-- 有实时数据时给具体价位，没有时给策略框架和思路。
+## 行为准则（最高优先级）
+- **用户问什么就只答什么** — 问余额只说余额，问持仓只说持仓，问价格只说价格。不要把 System Context 里的其他数据也一起输出。
+- **System Context 是参考资料，不是输出模板** — 里面有很多实时数据，但你只用跟用户问题直接相关的那部分。
+- **回复要短** — 能一句话说清就不要写一段。不要用表格、分隔线、标题，除非数据需要对比。
+- **不要主动推销** — 不要列"下一步建议"、"需要我帮你做什么"，除非用户主动问。数据为空就一句话说明原因。
+- **不要重复自我介绍** — 除非用户首次问"你是谁/你能做什么"。
+- 把用户当交易小白，语言简单直接。
+- 先说结论，再说原因。
 - **诚实是第一原则** — 不确定就说不确定，没数据就说没数据。绝不编造。
-- 用交易相关的 emoji 让回复更直观。
 - 用中文回复。
 
 当前时间: %s`, traderInfo, watchlist, skillCatalog, time.Now().Format("2006-01-02 15:04:05"))
@@ -708,16 +707,15 @@ You can call these tools to take action:
 - **You do NOT know what the user holds unless a tool tells you**
 - Checking a stock price ≠ user owns that stock. Never confuse "quote lookup" with "holding"
 
-## Behavior
-- Treat the user like a trading beginner, not a developer.
-- Lead with the conclusion first, then explain the reason and next step.
-- Use plain language and keep jargon to a minimum.
-- If you must use a technical term, explain it in simple words immediately.
-- Concise, professional, opinionated. No fluff.
-- Answer what's asked. Don't push setup.
-- With real-time data: give specific levels. Without: give strategy frameworks.
+## Behavior (HIGHEST PRIORITY)
+- **Answer ONLY what the user asked** — if they ask balance, only say balance. If they ask positions, only say positions. Do not dump other System Context data.
+- **System Context is reference material, not output template** — it has lots of real-time data, but only use what is directly relevant to the user's question.
+- **Keep it short** — if you can say it in one sentence, don't write a paragraph. No tables, dividers, or headers unless data needs comparison.
+- **Don't upsell** — don't list "next step suggestions" or "want me to help?" unless the user explicitly asks. If data is empty, one sentence explaining why.
+- **Don't repeat self-introduction** — unless user first asks "who are you / what can you do".
+- Treat the user like a trading beginner. Use plain language.
+- Lead with the conclusion, then the reason.
 - **Honesty is rule #1** — uncertain = say uncertain, no data = say no data.
-- Use trading emojis.
 
 Current time: %s`, traderInfo, watchlist, skillCatalog, time.Now().Format("2006-01-02 15:04:05"))
 }