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- th_10_shell.js: clean up outdated comments, title now 'Shell: broadcast execution'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_11_action.js

@@ -131,7 +131,7 @@ return;
     var r = this.execShellSmart(cmdB64, needRoot);
     if (r && r.ok) return;
 
-    this.toast("shell 失败（Action + 广播桥均失败）");
+    this.toast("shell 广播桥发送失败");
     safeLog(this.L, 'e',  "shell all failed cmd_b64=" + cmdB64 + " ret=" + JSON.stringify(r || {}));
     return;
   }