feat: expand to Tibetan + Theravada — 10 masters across 三大传统 (v0.4)

Adds the project's first non-Chinese masters, taking the scope from
"Chinese Buddhist" to "Buddhist" and matching the project name's
broader implication.

New masters
-----------
• prebuilt/milarepa — Tibetan Kagyu yogi (1052–1135). Sources:
  The Hundred Thousand Songs of Milarepa (mGur 'bum, BDRC W1KG14334)
  and The Life of Milarepa (rNam thar, BDRC W22272). Coverage:
  Mahāmudrā view, Naro Chodruk (name-level only — no esoteric steps),
  retreat & austerity, guru yoga, karma & purification.

• prebuilt/ajahn-chah — Thai Forest Tradition founder of Wat Pah Pong
  (1918–1992). Sources: Pali Canon (SuttaCentral SC IDs) plus
  authorized English collections Food for the Heart, A Still Forest
  Pool, Living Dhamma. Coverage: sati & satipaṭṭhāna, ānāpānasati,
  three characteristics, letting go, sīla-samādhi-paññā, middle way.

HARD-GATE additions
-------------------
• no_esoteric_instruction — Tibetan tantric practice steps (tummo,
  generation/completion stages, empowerment-required visualizations
  and mantras) are never disclosed; queries are redirected to
  qualified teachers. Boundary registered in
  scripts/validate-fidelity.py.

• No fabricated quotes for Theravāda discourses — Ajahn Chah quotes
  must trace to authorized publications; no synthesized "Ajahn Chah
  said" dialogue.

Citation system
---------------
BDRC:Wxxxxx (Tibetan canon) and SuttaCentral SC IDs are now
first-class alongside CBETA Txxnxxxx in frontmatter sources lists.
validate.py already accepts non-cbeta sources via the existing
title-or-cbeta_id check, no schema change required.

Cross-tradition compare-masters mappings
----------------------------------------
prebuilt/compare/SKILL.md gets new fallback rows for: 苦行/闭关
(xuyun + milarepa), 正念/觉知 (huineng + ajahn-chah + xuyun),
出离心/无常 (yinguang + milarepa + ajahn-chah), 三大传统对比
(huineng + milarepa + ajahn-chah), and adds milarepa to 般若/空性,
ajahn-chah to 戒律/行持.

Surface updates
---------------
• Description across package.json, .claude-plugin/{plugin,marketplace}.json,
  .cursor-plugin/plugin.json: "Chinese Buddhist" → "Buddhist",
  "8 prebuilt masters" → "10 prebuilt masters across 汉传/藏传/南传".
• README.md + README_EN.md: cross-tradition rows in the situational
  guidance table; new master cards for Milarepa and Ajahn Chah with
  appropriate provenance notes; v0.4 release banner replaces v0.3.
• SKILL.md preset list reorganized by tradition.
• CHANGELOG.md gets a [0.4.0] section.
• package.json keywords add tibetan-buddhism, theravada, bdrc,
  suttacentral.

Validation
----------
• python scripts/validate.py --strict → ✅ 11 masters pass
• python scripts/validate-fidelity.py → ✅ 11 masters validated
  (12 + 13 fidelity cases for the two new masters)
• python scripts/test-fidelity.py --all --dry-run → ✅
• pytest tests/ → ✅ 31 passed, 6 skipped

The progressive-disclosure shape of v0.3 is preserved exactly, so
the fidelity-smoke CI cost cap is unchanged.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

prebuilt/ajahn-chah/sources/INDEX.md

@@ -0,0 +1,24 @@
+# 阿姜查 Sources 索引
+
+本目录为离线可用的巴利经典与阿姜查公开开示集片段。
+
+## 收录文件
+
+| 文件 | 来源 | 标识 | 覆盖主题 |
+|---|---|---|---|
+| `sutta-excerpts.md` | 巴利三藏（Sutta Piṭaka） | SuttaCentral SC ID | 三法印、四念处、出入息念、戒定慧、中道 |
+| `teachings-excerpts.md` | 阿姜查公开开示集 | Food for the Heart / A Still Forest Pool / Living Dhamma | 正念、放下、心的训练、禅修、日常生活 |
+
+## 引用规范
+
+- **巴利经典**：`【SC: SN 22.59 / Anattalakkhaṇa Sutta】（SuttaCentral）`
+- **阿姜查开示**：`【《Food for the Heart》§Right Practice】`
+
+## 说明
+
+- 巴利经典片段引自 [SuttaCentral](https://suttacentral.net) 公开元数据；汉译参考庄春江、菩提比丘等多版本译本
+- 阿姜查开示集片段为 Wisdom Publications / Aruna Publications / 巴蓬寺正式英译授权出版物之主旨摘要，**非逐字英译重排**
+- 中文译本可参《阿姜查的禅修世界》（法园出版社）、《以法为赠礼》（嘉义新雨）等
+- 用于教学引用，不代表完整经义；深入研究请查阅 SuttaCentral 全文与上述出版物
+- **不收录违反阿姜查传承授权的内容**（如未公开许可的私下开示笔记）
+- 增补片段欢迎 PR