fix: panic when pressing * after the end of the file (#12611)

* fix: panic when pressing `*` at the end of the file

chore: remove incorrect additions

* docs: add info comment

* test: add new syntax to add a selection at the final character

* test: `*` panics when after the last char

* test: move into a more appopriate module

* test: fix failing

* test: account for Windows test suite

* test: choose a different strategy for custom syntax

* test: do not modify the syntax

* style: remove newline

---------

Co-authored-by: Nikita Revenco <154856872+NikitaRevenco@users.noreply.github.com>

helix-term/tests/test/commands.rs

@@ -6,6 +6,26 @@ mod insert;
 mod movement;
 mod write;
 
+#[tokio::test(flavor = "multi_thread")]
+async fn after_the_final_char() -> anyhow::Result<()> {
+    // <https://github.com/helix-editor/helix/issues/12609>
+    test((
+        indoc! {"\
+            #[o|]#ne
+            two
+            three"},
+        "gej*h",
+        indoc! {"\
+            one
+            two
+            three#[
+            |]#"},
+    ))
+    .await?;
+
+    Ok(())
+}
+
 #[tokio::test(flavor = "multi_thread")]
 async fn test_selection_duplication() -> anyhow::Result<()> {
     // Forward