test(makefile): use --clean for isolated test runs (#1338)

Switches the test target to use `nvim --headless --clean` instead of
`--noplugin` to ensure tests run in a fully isolated environment,
avoiding interference from user or system configuration. This improves
test reliability and consistency.

Author: deathbeam

Makefile

@@ -24,7 +24,7 @@ install-pre-commit:
 	pre-commit install
 
 test:
-	nvim --headless --noplugin -u ./scripts/test.lua
+	nvim --headless --clean -u ./scripts/test.lua
 
 all: luajit