Set .Platform$GUI to "Positron" in console sessions only (#977)

* Set `.Platform$GUI` to "Positron" in console sessions only

* Add simple test

* Revert "Add simple test"

This reverts commit b78ba94.

* Revert "Set `.Platform$GUI` to "Positron" in console sessions only"

This reverts commit e5ae05b.

* Set `.Platform$GUI` just in the positron module

* This all gets evaluated outside of Positron as well

* Update crates/ark/src/modules/positron/positron.R

Co-authored-by: Lionel Henry <[email protected]>

---------

Co-authored-by: Lionel Henry <[email protected]>

Author: juliasilge

crates/ark/src/modules/positron/positron.R

@@ -0,0 +1,12 @@
+#
+# positron.R
+#
+# Copyright (C) 2025 Posit Software, PBC. All rights reserved.
+#
+#
+
+if (Sys.getenv("POSITRON") == 1) {
+    .Platform <- base::.Platform
+    .Platform$GUI <- "Positron"
+    env_bind_force(baseenv(), ".Platform", .Platform)
+}