scripting_tool: Move description into a separate file (#26283)

This PR moves the `scripting_tool` description into a separate file so
it's a bit easier to work with.

Release Notes:

- N/A

crates/scripting_tool/src/scripting_tool.rs

@@ -27,20 +27,7 @@ impl Tool for ScriptingTool {
     }
 
     fn description(&self) -> String {
-        r#"You can write a Lua script and I'll run it on my code base and tell you what its output was,
-including both stdout as well as the git diff of changes it made to the filesystem. That way,
-you can get more information about the code base, or make changes to the code base directly.
-The lua script will have access to `io` and it will run with the current working directory being in
-the root of the code base, so you can use it to explore, search, make changes, etc. You can also have
-the script print things, and I'll tell you what the output was. Note that `io` only has `open`, and
-then the file it returns only has the methods read, write, and close - it doesn't have popen or
-anything else. Also, I'm going to be putting this Lua script into JSON, so please don't use Lua's
-double quote syntax for string literals - use one of Lua's other syntaxes for string literals, so I
-don't have to escape the double quotes. There will be a global called `search` which accepts a regex
-(it's implemented using Rust's regex crate, so use that regex syntax) and runs that regex on the contents
-of every file in the code base (aside from gitignored files), then returns an array of tables with two
-fields: "path" (the path to the file that had the matches) and "matches" (an array of strings, with each
-string being a match that was found within the file)."#.into()
+        include_str!("scripting_tool_description.txt").into()
     }
 
     fn input_schema(&self) -> serde_json::Value {