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/dev-environment-setup/references/decision-tree.md

@@ -35,14 +35,14 @@
 
 **触发条件**
 
-- `~/.desirecore/agent-service.port` 文件存在且可读
+- `${DESIRECORE_ROOT}/agent-service.port` 文件存在且可读
 - `curl -sk --max-time 0.5 https://127.0.0.1:${PORT}/api/runtime/environment` 返回 2xx
 - 当前会话能订阅 Socket.IO（DesireCore 内部 Agent 默认满足）
 
 **典型操作**
 
 ```bash
-PORT=$(cat ~/.desirecore/agent-service.port)
+PORT=$(cat ${DESIRECORE_ROOT}/agent-service.port)
 BASE="https://127.0.0.1:${PORT}/api/runtime"
 
 # 1. 拉取快照
@@ -74,11 +74,11 @@ curl -sk -X POST "${BASE}/python/install" \
 **典型操作（macOS / Linux）**
 
 ```bash
-HATCH=~/.desirecore/runtime/hatch/hatch
-VOLTA=~/.desirecore/runtime/volta/volta
+HATCH=${DESIRECORE_ROOT}/runtime/hatch/hatch
+VOLTA=${DESIRECORE_ROOT}/runtime/volta/volta
 
-export HATCH_HOME=~/.desirecore/runtime/hatch
-export VOLTA_HOME=~/.desirecore/runtime/volta
+export HATCH_HOME=${DESIRECORE_ROOT}/runtime/hatch
+export VOLTA_HOME=${DESIRECORE_ROOT}/runtime/volta
 
 "$HATCH" python install 3.12
 "$VOLTA" install node@22