Expand stdio command help text with examples, log behavior, and usage guidance (#1551)

* Initial plan

* Expand stdio command help text with description, examples, and log/error behavior

Co-authored-by: waldekmastykarz <11164679+waldekmastykarz@users.noreply.github.com>

* Apply suggestion from @waldekmastykarz

* Align example descriptions to the same column position

Co-authored-by: waldekmastykarz <11164679+waldekmastykarz@users.noreply.github.com>

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: waldekmastykarz <11164679+waldekmastykarz@users.noreply.github.com>
Co-authored-by: Waldek Mastykarz <waldek@mastykarz.nl>
Co-authored-by: Garry Trinder <garry@trinder365.co.uk>

Author: 3 people

DevProxy/Commands/DevProxyConfigOptions.cs

@@ -178,7 +178,19 @@ public DevProxyConfigOptions()
                 return value;
             }
         };
-        var stdioCommand = new Command("stdio", "Proxy stdin/stdout/stderr of local executables")
+        var stdioCommand = new Command("stdio", """
+            Proxy stdin/stdout/stderr of local executables.
+            Dev Proxy intercepts and processes the stdio streams of the specified command,
+            applying configured plugins (mocking, error simulation, etc.) to the traffic.
+            Logs are written to a timestamped file (devproxy-stdio-YYYYMMDD-HHmmss.log)
+            to avoid interfering with the proxied streams.
+            Usage errors and exceptions are written to stderr.
+
+            Examples:
+              devproxy stdio npx -y @devproxy/mcp          Proxy MCP server
+              devproxy stdio node server.js                Proxy Node.js app
+              devproxy stdio -c myconfig.json node app.js  With custom config
+            """)
         {
             stdioConfigFileOption,
             // Add a catch-all argument to consume remaining args (command to execute)

DevProxy/Commands/StdioCommand.cs

@@ -32,7 +32,19 @@ public StdioCommand(
         ILogger<StdioCommand> logger,
         ILoggerFactory loggerFactory,
         IEnumerable<IStdioPlugin> plugins) :
-        base("stdio", "Proxy stdin/stdout/stderr of local executables")
+        base("stdio", """
+            Proxy stdin/stdout/stderr of local executables.
+            Dev Proxy intercepts and processes the stdio streams of the specified command,
+            applying configured plugins (mocking, error simulation, etc.) to the traffic.
+            Logs are written to a timestamped file (devproxy-stdio-YYYYMMDD-HHmmss.log)
+            to avoid interfering with the proxied streams.
+            Usage errors and exceptions are written to stderr.
+
+            Examples:
+              devproxy stdio npx -y @devproxy/mcp          Proxy MCP server
+              devproxy stdio node server.js                Proxy Node.js app
+              devproxy stdio -c myconfig.json node app.js  With custom config
+            """)
     {
         _logger = logger;
         _loggerFactory = loggerFactory;