移除 Docker 构建路线，改为 host 直装 Qt 5.14.2 + Qt Creator 4.11.0

学生主要用 Windows，Docker 方案不再需要：删掉 tools/docker/ 及 README/HANDOFF/
CMakeLists 里的相关引用（含一处已失效的 docker_run.sh 死链接）。

install_qt_host.sh 现在同时装期号匹配的 Qt Creator 4.11.0：官方 .run 安装器
强制要求 Qt 账号登录且无 Skip 选项，改用 tools/extract_qtcreator_payload.py
直接从 .run 里定位、解出内嵌的 7z payload，绕开账号登录。提取逻辑先解到
staging 目录再原子替换到位，避免中途失败留下部分安装但被判定为"已装"；
候选 7z 复用同一临时文件，不会在磁盘上堆多份安装包大小的临时拷贝。

tools/run_qtcreator.sh

@@ -0,0 +1,13 @@
+#!/usr/bin/env bash
+# Launch the ISOLATED Qt Creator 4.11.0 installed into .qt514/Tools/QtCreator
+# (period-matched to the isolated Qt 5.14.2 SDK), wired to open this repo's
+# CMakeLists.txt against .qt514/ by default.
+#   Usage: tools/run_qtcreator.sh [args...]
+# -settingspath keeps this Creator's config separate from any system/other
+# Qt Creator install on the host (avoids config-format crashes across versions).
+set -euo pipefail
+REPO_ROOT="$(cd "$(dirname "${BASH_SOURCE[0]}")/.." && pwd)"
+QT_ROOT="$REPO_ROOT/.qt514/5.14.2/gcc_64"
+CREATOR_BIN="$REPO_ROOT/.qt514/Tools/QtCreator/bin/qtcreator"
+export CMAKE_PREFIX_PATH="$QT_ROOT${CMAKE_PREFIX_PATH:+:$CMAKE_PREFIX_PATH}"
+exec "$CREATOR_BIN" -settingspath "$REPO_ROOT/.qt514/qtcreator-settings" "$@"