feat(v0.6): namespace all 14 master slash commands under /master-<slug> prefix

Slash command discoverability cleanup. Claude Code users typically have
50+ skills installed; bare-word commands like /atisha and /zhiyi got
scattered across the /-completion list. v0.6 prefixes all 14 master
slash commands with master- so they cluster under /m<tab> and clearly
signal "this is a Master-skill master skill".

Scope of rename
---------------
* Slash commands: /zhiyi → /master-zhiyi, /huineng → /master-huineng,
  ... all 14 affected.
* Directory layout: prebuilt/<slug>/ → prebuilt/master-<slug>/ for all
  14 masters (git mv preserves history).
* Frontmatter: each prebuilt/master-<slug>/SKILL.md updates `name:` to
  master-<slug>.
* compare-masters and create-master meta-skills are intentionally
  unchanged — they're already prefixed by their nature, and
  /master-compare-masters would be doublespeak.

Decoupling: fojin.app/chat is NOT affected
------------------------------------------
The fojin web frontend's master dropdown uses bare slug IDs (atisha,
huineng, ...) and is already grouped under "法师模式" in its UI. Backend
master_profiles.py keeps `id="atisha"` etc. unchanged. No fojin-side
migration required. The two surfaces (Claude Code slash + fojin
dropdown) are now formally decoupled by design, not coincidence.

Compatibility
-------------
* NPX installer accepts both forms: `npx master-skill install zhiyi`
  (short) and `install master-zhiyi` (full) both resolve to the same
  prebuilt/master-zhiyi/ source. Install destination is always
  ~/.claude/skills/master-<slug>/. Backward-compatible uninstall
  handles legacy non-prefixed installs (~/.claude/skills/zhiyi/).
* The cli.mjs already used `master-${name}` for install destinations
  (since v0.3 NPX installer was added), so existing v0.4/v0.5 NPX
  users were already getting the prefix in skills/ — only the source
  prebuilt/ layout and slash commands change in v0.6.

Files updated
-------------
* 14 directories renamed (28 files moved, 0 content changes).
* 14 SKILL.md frontmatter `name:` fields.
* prebuilt/compare/SKILL.md: 43 slug references updated to prefixed form.
* bin/cli.mjs: resolveMasterDir helper accepts both short and full;
  cmdInstall and cmdUninstall handle legacy paths.
* .github/workflows/validate-and-test.yml: fidelity-smoke MASTERS
  rotation array updated to all 14 prefixed names (was 8 hardcoded
  汉传 only — now properly rotates across the full set).
* scripts/{validate,cite,query,test-fidelity}.py: --master arg help
  text examples.
* README.md + README_EN.md: situational guidance table, install
  snippets, master cards. New v0.6 release banner.
* SKILL.md (project-level) preset list with new slash names.
* ETHICS.md Tier table slug references (4).
* All plugin manifests bumped 0.5.0 → 0.6.0 with description noting
  the /master-<slug> invocation pattern.
* CHANGELOG.md: [0.6.0] section with breaking-change notice and
  migration commands for existing NPX users.

Validation
----------
* python scripts/validate.py --strict           ✓ 15 masters pass
* python scripts/validate-fidelity.py           ✓ all valid
* python scripts/test-fidelity.py --all --dry-run  ✓
* pytest tests/                                  ✓ 31 passed, 6 skipped
* node bin/cli.mjs list                          ✓ shows all 14 with
                                                   master- prefix
* node bin/cli.mjs install zhiyi                 ✓ resolves to
                                                   prebuilt/master-zhiyi/
* node bin/cli.mjs install master-zhiyi          ✓ resolves to same

Migration for existing v0.4/v0.5 users
--------------------------------------
    npx master-skill@0.5 uninstall zhiyi huineng xuanzang ...
    # OR: rm -rf ~/.claude/skills/{zhiyi,huineng,...}
    npx master-skill@latest install --all

Then start a new Claude Code session; the new slash commands are
/master-zhiyi, /master-huineng, etc.

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

CONTRIBUTING.md

@@ -63,7 +63,7 @@ python scripts/validate-fidelity.py
 python scripts/test-fidelity.py --all --dry-run
 
 # Fidelity 实跑（需要 ANTHROPIC_API_KEY，一次 ≈ $0.05-0.10）
-ANTHROPIC_API_KEY=sk-... python scripts/test-fidelity.py --master zhiyi --max-tests 1
+ANTHROPIC_API_KEY=sk-... python scripts/test-fidelity.py --master master-zhiyi --max-tests 1
 ```
 
 ---
@@ -128,10 +128,10 @@ ANTHROPIC_API_KEY=sk-... python scripts/test-fidelity.py --master zhiyi --max-te
 
 ### 3.3 选项 B：手工编写
 
-参考现有法师 `prebuilt/yinguang/` 的完整结构：
+参考现有法师 `prebuilt/master-yinguang/` 的完整结构：
 
 ```
-prebuilt/<slug>/
+prebuilt/master-<slug>/
 ├── SKILL.md             # 必须。frontmatter 见下
 ├── meta.json            # 必须。search_scope + keywords
 ├── references/
@@ -174,7 +174,10 @@ verified_at: <YYYY-MM-DD>
 
 ### 3.4 Voice.md 四层结构
 
-见 `prebuilt/yinguang/references/voice.md` 作为参照。重点：
+见 `prebuilt/master-yinguang/references/voice.md` 作为参照。重点：
+
+> ⚠️ **v0.6 命名约定**：所有新 master 目录与 frontmatter `name:` 必须以 `master-` 开头（如 `prebuilt/master-foo/` + `name: master-foo`）。两个 meta-skill 例外：`compare-masters` 与 `create-master` 保持原状（避免 `/master-compare-masters` 重复前缀）。详见 [CHANGELOG §0.6.0](CHANGELOG.md#060--2026-05-02)。
+
 
 - **Layer 0 — 硬规则**：[`ETHICS.md` §3](ETHICS.md) 的禁止行为必须原文复制到此
 - **Layer 1 — 身份**：生卒、传承、核心立场