fix(frontmatter): 修正 maintain 技能 SKILL.md frontmatter 的 YAML 純量語法錯誤

What：
- 修正 skills/maintain/SKILL.md frontmatter 裡 description 欄位的 YAML 語法錯誤。
- 整串 description 加上單引號，內部撇號改寫成兩個單引號，內容文字一個字都沒變。
- 同步更新 plugin.json、.claude-plugin/plugin.json、.codex-plugin/plugin.json 三個 manifest 版本號，從 0.2.7 進到 0.2.8。

Why：
- description 內含「冒號加空白」，屬於未加引號的 YAML plain scalar，違反 YAML 語法規定。
- Antigravity 解析 frontmatter 時當場中斷，整支技能被靜默丟棄，沒有任何錯誤訊息；磁碟上 34 支技能，Antigravity 只認得 28 支。
- 準則要求 description 用英文撰寫，不能把「: 」改成全形冒號迴避語法問題，只能加引號修正。

How：
- 整串 description 值加上單引號，內部撇號寫成兩個單引號跳脫，其餘字元不動。
- 用 git show HEAD: 取出改前的原始值，把改後的單引號純量還原後做字串相等比對，確認逐字相同、字元數一致。
- 執行 ste100-lint.sh、check-behaviors.sh、lint-frontmatter.sh 三支檢查腳本，退出碼皆為 0；git diff --numstat 顯示只動了 frontmatter 那一行。

Who：
- 本次修到 sdlc 技能組的 maintain 技能，屬 SDLC 維運階段、定期維護已交付專案的功能。

.claude-plugin/plugin.json

@@ -1,6 +1,6 @@
 {
   "name": "jsc-sdlc",
-  "version": "0.2.7",
+  "version": "0.2.8",
   "description": "開發生命週期：規劃、分析、實作、維護（wiki 追蹤）",
   "skills": "./skills",
   "author": {

.codex-plugin/plugin.json

@@ -1,6 +1,6 @@
 {
   "name": "jsc-sdlc",
-  "version": "0.2.7",
+  "version": "0.2.8",
   "description": "開發生命週期：規劃、分析、實作、維護（wiki 追蹤）",
   "skills": "./skills",
   "jsc": {

plugin.json

@@ -1,6 +1,6 @@
 {
   "name": "jsc-sdlc",
-  "version": "0.2.7",
+  "version": "0.2.8",
   "description": "開發生命週期：規劃、分析、實作、維護（wiki 追蹤）",
   "skills": "./skills/",
   "jsc": {

skills/maintain/SKILL.md

@@ -1,6 +1,6 @@
 ---
 name: maintain
-description: SDLC maintenance stage. Gate on capability tags enforced in code by sdlc-gate (maintenance requires no specific tag, but the actual model id must be determinable from the transcript), read projects still inside their maintenance window from MAINTAIN_CONTENTS, then run one sub agent per project: switch to develop or master, propose at least five maintenance actions, commit to a new branch, push, and PR. Write a jsc-log:worklog entry per finished project and update the last-maintained timestamp afterward, then close with tools/stage-report.sh - model tag verdict, worklog link, every wiki link written. Use for periodic upkeep of delivered projects inside their maintenance window; not for projects still mid-implementation or not yet registered in MAINTAIN_CONTENTS.
+description: 'SDLC maintenance stage. Gate on capability tags enforced in code by sdlc-gate (maintenance requires no specific tag, but the actual model id must be determinable from the transcript), read projects still inside their maintenance window from MAINTAIN_CONTENTS, then run one sub agent per project: switch to develop or master, propose at least five maintenance actions, commit to a new branch, push, and PR. Write a jsc-log:worklog entry per finished project and update the last-maintained timestamp afterward, then close with tools/stage-report.sh - model tag verdict, worklog link, every wiki link written. Use for periodic upkeep of delivered projects inside their maintenance window; not for projects still mid-implementation or not yet registered in MAINTAIN_CONTENTS.'
 ---
 
 # maintain