feat: 初始提交 LeonOS 实现

添加 LeonOS 的基本实现，包括：
- 核心 API 模块（colors, disk, gps, keys, multishell, parallel, rednet, redstone, settings, vector）
- 命令行程序（about, alias, bg, clear, copy, delete, edit, fg, help, list, lua, mkdir, move, paint, peripherals, programs, reboot, set, shutdown, threads）
- 系统启动脚本和包管理
- 文档（README.md, LICENSE）
- 开发工具（devbin）和更新程序

实现功能：
- 完整的线程管理系统
- 兼容 ComputerCraft 的 API 设计
- 改进的 shell 和命令补全系统
- 多标签终端支持
- 设置管理系统

data/computercraft/lua/rom/programs/shell.lua

@@ -0,0 +1,79 @@
+-- rc.shell
+
+local rc = require("rc")
+local fs = require("fs")
+local term = require("term")
+local shell = require("shell")
+local colors = require("colors")
+local thread = require("rc.thread")
+local textutils = require("textutils")
+
+if os.version then
+  textutils.coloredPrint(colors.yellow, os.version(), colors.white)
+else
+  textutils.coloredPrint(colors.yellow, rc.version(), colors.white)
+end
+
+thread.vars().parentShell = thread.id()
+shell.init(_ENV)
+
+if not shell.__has_run_startup then
+  shell.__has_run_startup = true
+  if fs.exists("/startup.lua") then
+    local ok, err = pcall(dofile, "/startup.lua")
+    if not ok and err then
+      io.stderr:write(err, "\n")
+    end
+  end
+
+  if fs.exists("/startup") and fs.isDir("/startup") then
+    local files = fs.list("/startup/")
+    table.sort(files)
+
+    for f=1, #files, 1 do
+      local ok, err = pcall(dofile, "/startup/"..files[f])
+      if not ok and err then
+        io.stderr:write(err, "\n")
+      end
+    end
+  end
+end
+
+local aliases = {
+  background = "bg",
+  clr = "clear",
+  cp = "copy",
+  dir = "list",
+  foreground = "fg",
+  mv = "move",
+  rm = "delete",
+  rs = "redstone",
+  sh = "shell",
+  ps = "threads"
+}
+
+for k, v in pairs(aliases) do
+  shell.setAlias(k, v)
+end
+
+local completions = "/rc/completions"
+for _, prog in ipairs(fs.list(completions)) do
+  dofile(fs.combine(completions, prog))
+end
+
+local history = {}
+while true do
+  term.setTextColor(colors.yellow)
+  term.setBackgroundColor(colors.black)
+  rc.write(colors.yellow.."$"..shell.dir()..colors.green.." >>> ")
+  term.setTextColor(colors.white)
+
+  local text = term.read(nil, history, shell.complete)
+  if #text > 0 then
+    history[#history+1] = text
+    local ok, err = shell.run(text)
+    if not ok and err then
+      io.stderr:write(err, "\n")
+    end
+  end
+end