Drop make install from the required targets; test three more stops

The install target stays in this repo's Makefile only. sneak/vaultik
already has an install target with another meaning, and every repo
still gets script/install.

Tests: a repo's own script/update-policy stops the script, and a repo
whose only JavaScript source is a .js or .mjs file gets the JavaScript
style guide.

Model: opus-5-5

test/update-policy.sh

@@ -453,6 +453,21 @@ test_language_files_need_a_source_file() {
     expect_new_commit_not_pushed
 }
 
+test_javascript_source_brings_its_styleguide() {
+    for extension in js mjs; do
+        start_scenario "a repo whose only JavaScript source is a .$extension file gets the JavaScript style guide"
+        echo "export {}" > "$dir/repo/web.$extension"
+        commit_and_push_fixture "web.$extension"
+        remove_from_fixture docs/CODE_STYLEGUIDE_JS.md
+        run_update_policy
+        expect_success
+        expect_file docs/CODE_STYLEGUIDE_JS.md << 'EOF'
+new CODE_STYLEGUIDE_JS
+EOF
+        expect_new_commit_not_pushed
+    done
+}
+
 test_nothing_changed() {
     start_scenario "nothing changed"
     cp "$dir/canonical/.prettierrc" "$dir/repo/.prettierrc"
@@ -675,14 +690,16 @@ EOF
 }
 
 test_own_script_stops() {
-    start_scenario "a tracked script/install with a line the canonical file has never held stops"
-    echo "echo our own installer" >> "$dir/repo/script/install"
-    commit_and_push_fixture .prettierrc
-    run_update_policy
-    expect_failure
-    expect_output "script/install has lines"
-    expect_output "echo our own installer"
-    expect_nothing_written
+    for script in script/install script/update-policy; do
+        start_scenario "a tracked $script with a line the canonical file has never held stops"
+        echo "echo our own script" >> "$dir/repo/$script"
+        commit_and_push_fixture .prettierrc
+        run_update_policy
+        expect_failure
+        expect_output "$script has lines"
+        expect_output "echo our own script"
+        expect_nothing_written
+    done
 }
 
 test_gitignore_lacks_canonical_last_line() {
@@ -827,6 +844,7 @@ main() {
     test_own_entries_kept
     test_files_the_repo_lacks_are_written_whole
     test_language_files_need_a_source_file
+    test_javascript_source_brings_its_styleguide
     test_nothing_changed
     test_target_lacking_install_gets_both_scripts
     test_update_policy_replaces_itself