Add configuration option jetbrains_launch_command, allowing Serena to spawn IDE instances automatically

upon project activation

Serena searches for the plugin instance upon project activation, and if the instance is not found
and the setting is configured, launches a new IDE instance based on the command

docs/02-usage/025_jetbrains_plugin.md

@@ -84,7 +84,7 @@ language_backend: JetBrains
 
 Note that the file might not exist yet if you never executed Serena before.
 
-**Per-Server Instance Configuration**.
+**Per-Instance Configuration**.
 The configuration setting in the global config file can be overridden on a
 per-instance basis by providing the arguments `--language-backend JetBrains` when
 launching the Serena MCP server.
@@ -121,8 +121,12 @@ You will also notice that your client will use the JetBrains-specific tools like
 
 Having installed the plugin in your IDE and having configured Serena to use the JetBrains backend,
 the general workflow is simple:
+
 1. Open the project you want to work on in your JetBrains IDE.  
-   Note that the project must be appropriately set up in your IDE, i.e. symbol lookups for all relevant programming languages and frameworks should work in the IDE.
+   Note that the project must be appropriately set up in your IDE, i.e. symbol lookups for all relevant programming languages and frameworks should work in the IDE.  
+
+   You can optionally make Serena open an IDE instance for your project root folder automatically upon project activation, allowing you to skip this step for a project that was previously set up correctly.
+   To enable this, configure `jetbrains_launch_command` in [Serena's global configuration file](global-config) appropriately.
 2. Activate the project's root folder as a project in Serena (see [Project Creation](project-creation-indexing) and [Project Activation](project-activation)).
 3. Start using Serena's tools as usual.