feat: 新增 jsc-matt 外掛，收錄 Matt Pocock 全套技能，指令為 /jsc-matt:*

- 改編自 mattpocock/skills 1.2.3（MIT），含 engineering 與 productivity 共 25 個技能
- 技能間的呼叫名稱一律加上 jsc-matt: 前綴
- marketplace 與 README 補上 jsc-matt

Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>

plugins/jsc-matt/skills/engineering/diagnosing-bugs/scripts/hitl-loop.template.sh

@@ -0,0 +1,44 @@
+#!/usr/bin/env bash
+# Human-in-the-loop reproduction loop.
+# Copy this file, edit the steps below, and run it.
+# The agent runs the script; the user follows prompts in their terminal.
+#
+# Usage:
+#   bash hitl-loop.template.sh
+#
+# Two helpers:
+#   step "<instruction>"          → show instruction, wait for Enter
+#   capture VAR "<question>"      → show question, read response into VAR
+#
+# At the end, captured values are printed as KEY=VALUE for the agent to parse.
+#
+# `capture` prints its value back to the terminal, where the agent reads it,
+# so capture observations, and leave signing in to the user as a `step`.
+
+set -euo pipefail
+
+step() {
+  printf '\n>>> %s\n' "$1"
+  read -r -p "    [Enter when done] " _
+}
+
+capture() {
+  local var="$1" question="$2" answer
+  printf '\n>>> %s\n' "$question"
+  read -r -p "    > " answer
+  printf -v "$var" '%s' "$answer"
+}
+
+# --- edit below ---------------------------------------------------------
+
+step "Open the app at http://localhost:3000 and sign in."
+
+capture ERRORED "Click the 'Export' button. Did it throw an error? (y/n)"
+
+capture ERROR_MSG "Paste the error message (or 'none'):"
+
+# --- edit above ---------------------------------------------------------
+
+printf '\n--- Captured ---\n'
+printf 'ERRORED=%s\n' "$ERRORED"
+printf 'ERROR_MSG=%s\n' "$ERROR_MSG"