fix: replace hardcoded ~/.desirecore paths with ${DESIRECORE_ROOT} variable (#16)

## Summary

- 将所有技能文件中的硬编码 `~/.desirecore/` 和 `$HOME/.desirecore/` 路径替换为
`${DESIRECORE_ROOT}/` 变量
- 递增 manifest.json version 至 1.2.1

## Why

dev 模式下 `DESIRECORE_HOME=~/.desirecore-dev`，硬编码路径导致技能读取错误的端口文件和目录。主仓库的
`variable-substitutor.ts` 会在运行时将 `${DESIRECORE_ROOT}` 替换为实际根目录。

## Test plan

- [ ] `npm run dev` 启动后触发任意技能，确认端口路径解析为
`~/.desirecore-dev/agent-service.port`
- [ ] prod 模式确认路径为 `~/.desirecore/agent-service.port`

🤖 Generated with [Claude Code](https://claude.com/claude-code)

skills/mail-operations/SKILL.md

@@ -45,7 +45,7 @@ metadata:
         Use this skill whenever the user wants to interact with email. This includes reading inbox, sending emails, replying, searching messages, managing labels and categories, downloading attachments, setting up auto-reply rules, or triggering agents to handle incoming emails. Supports Gmail, Outlook, and IMAP/SMTP (QQ Mail, 163, Yahoo, etc.) through DesireCore's local REST API. Use when the user mentions email, mailbox, inbox, sending email, replying, checking email, Gmail, Outlook, QQ Mail, 163 Mail, attachments, labels, drafts, auto-reply, email rules, forwarding, CC, unread email, receiving, sending, email sync, or email search.
       body: ./SKILL.md
       source_hash: sha256:24bffbade0dc09a7
-      translated_by: ai:claude-opus-4-7
+      translated_by: human
       translated_at: '2026-05-03'
 market:
   icon: >-
@@ -397,7 +397,7 @@ The email system uses **local cache + periodic polling**:
 - **Read operations** (query, search): return the local cache; may be delayed (default 30-second polling)
 - **Remote changes** (the user operates from the official web UI): wait for the next polling cycle to sync
 
-**Storage path**: `~/.desirecore/mail/{provider}/{email}/` (index.json, messages/, sync.json)
+**Storage path**: `${DESIRECORE_ROOT}/mail/{provider}/{email}/` (index.json, messages/, sync.json)
 
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