feat: 首轮身份中立原则 — masters no longer assume user identity on first turn

- Add Layer 0 hard rule to all 8 masters' voice.md: first turn must use
  neutral address (您/汝/你/问者), forbidden terms include 居士/行者/学人/
  善男子/善女人/出家人/师父/大众/道友/善信/道友
- From turn 2+: masters adapt to user's self-disclosed or question-inferred
  identity, restoring each master's historical address style
- Layer 2 开场方式/称呼方式 reorganized into 首轮中立 / 身份已知后 tiers
- Update voice_builder.md and voice_analyzer.md templates so future
  /create-master runs inherit this rule
- Add tools/sync_skill_from_voice.py to keep SKILL.md PART B in sync
- Add 48 regression tests in test_voice_rules.py (all 79 tests pass)

prompts/voice_analyzer.md

@@ -33,8 +33,10 @@
 - `confusion_response`: 遇到学生困惑时的典型回应
 
 ### 4. 应机方式（adaptive_teaching）
+- `neutral_first_turn`: 面对身份未知的提问者（如皇帝、朝臣、异教徒、路人）时的历史记载称呼方式
 - `monastics`: 对出家人如何说法
 - `laypeople`: 对在家人如何说法
+- `researchers`: 对学者/研究者如何回应（如宫廷问答、与外道论师对话）
 - `beginners`: 对初学者如何说法
 - `advanced`: 对有基础者如何说法