Clarify custom shell and self-hosted server usage in README (#308)

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>

Author: Copilot

README.md

@@ -42,20 +42,40 @@ scoop install powersession-rs
 ### Get Help
 ```console
 PS D:\projects\PowerSession> PowerSession.exe -h
-PowerSession
+Usage: PowerSession [OPTIONS] <COMMAND>
+
+Commands:
+  rec     Record and save a session
+  play    Play a recorded session
+  auth    Authentication with api server (default is asciinema.org)
+  upload  Upload a session to api server
+  server  The url of asciinema server
+  stream  Stream a live terminal session to the asciinema server
+  help    Print this message or the help of the given subcommand(s)
+
+Options:
+  -l, --log-level <log-level>  can be one of [error|warn|info|debug|trace] [default: error]
+  -h, --help                   Print help
+  -V, --version                Print version
+```
+
+### Record with a specific shell or startup arguments
 
-USAGE:
-    PowerSession.exe [SUBCOMMAND]
+Use `-c` / `--command` to choose the shell explicitly and include any startup arguments you need.
 
-OPTIONS:
-    -h, --help    Print help information
+```console
+PowerSession.exe rec demo.cast --command "powershell.exe -NoLogo"
+PowerSession.exe rec demo.cast --command "pwsh.exe -NoLogo"
+```
 
-SUBCOMMANDS:
-    rec       Record and save a session
-    play
-    auth      Authentication with asciinema.org
-    upload    Upload a session to ascinema.org
-    help      Print this message or the help of the given subcommand(s)
+### Use a self-hosted asciinema server
+
+Set the server URL once, then authenticate and upload as usual. The configured server is reused for `auth`, `upload`, and `stream`.
+
+```console
+PowerSession.exe server https://asciinema.example.com
+PowerSession.exe auth
+PowerSession.exe upload demo.cast
 ```
 
 ## Credits

src/commands/api/asciinema.rs

@@ -24,6 +24,10 @@ struct Config {
 }
 
 impl Config {
+    fn new_config_notice() -> String {
+        "New config file created \nDefault instance will be used: https://asciinema.org \nTo set a custom server run: PowerSession.exe server <url>\n".to_string()
+    }
+
     fn get_config_file() -> (PathBuf, PathBuf) {
         let app_dirs = AppDirs::new(None, true).unwrap();
         let config_root = app_dirs.config_dir.join("PowerSession");
@@ -40,11 +44,7 @@ impl Config {
             c.location = config_file.to_str().unwrap().to_owned();
             c
         } else {
-            let text = format!(
-                "New config file created \nDefault instance will be used: https://asciinema.org \nTo set a custom server type: PowerSession.exe --server <hostname>\n"
-            );
-
-            println!("{}", text);
+            println!("{}", Self::new_config_notice());
             return Self::new(None);
         };
     }
@@ -315,4 +315,12 @@ mod tests {
         let expected = format!("Basic {}", BASE64_STANDARD.encode("user:token-123"));
         assert_eq!(asc.get_auth_header(), expected);
     }
+
+    #[test]
+    fn test_new_config_notice_mentions_server_subcommand() {
+        let notice = Config::new_config_notice();
+
+        assert!(notice.contains("PowerSession.exe server <url>"));
+        assert!(!notice.contains("--server"));
+    }
 }