refactor: remove Action-first shell path, keep only broadcast bridge

- th_10_shell.js: clean up outdated comments, title now 'Shell: broadcast execution'
- th_11_action.js: update toast msg from 'Action + bridge both failed' to 'broadcast bridge send failed'
- th_01_base.js: remove 'Action-first path' reference in Base64 decode comment
- th_16_entry.js already has useActionFirst: false / hasShellCommand: false

code/th_01_base.js

@@ -1097,7 +1097,7 @@ function getProcessInfo(tag) {
 
 
 // =======================【工具：Base64 解码（UTF-8）】=======================
-// # 这段代码的主要内容/用途：把 cmd_b64 还原成原始 shell 文本（仅用于 Action 优先路径；广播桥永远传 b64）
+// # 这段代码的主要内容/用途：把 cmd_b64 还原成原始 shell 文本
 function decodeBase64Utf8(b64) {
   try {
     var s = String(b64 || "");