run_tests: Stop treating non-workspace dirs as packages (#60502)

The `orchestrate` job maps changed directories to root-workspace package
names, and when no mapping was found it fell back to using the raw
directory name as a package. Because `tooling/lints` is a separate
workspace (not a root-workspace member), a change under
`tooling/lints/**` produced the filter `rdeps(lints)`, which `cargo
nextest run --workspace` rejects with "operator didn't match any
packages" — failing `run_tests` for any such PR. This drops that
fallback so an unmapped directory falls through to the existing "no
package changes → run all tests" path instead.

Release Notes:

- N/A

.github/workflows/run_tests.yml

@@ -76,11 +76,16 @@ jobs:
           FILE_CHANGED_PKGS=""
           for dir in $CHANGED_DIRS; do
             pkg=$(echo "$DIR_TO_PKG" | grep "^${dir}=" | cut -d= -f2 | head -1 || true)
+            # Only add directories that map to a real root-workspace package.
+            # Some directories (e.g. tooling/lints) belong to a separate workspace
+            # and are not root members, so they have no mapping here. Previously we
+            # fell back to the raw directory name, which fabricated a bogus package
+            # (e.g. "lints") and produced a nextest filter like rdeps(lints) that
+            # hard-errors ("operator didn't match any packages"). Skipping such
+            # directories leaves the package set empty, which falls through to the
+            # "run all tests" path below.
             if [ -n "$pkg" ]; then
               FILE_CHANGED_PKGS=$(printf '%s\n%s' "$FILE_CHANGED_PKGS" "$pkg")
-            else
-              # Fall back to directory name if no mapping found
-              FILE_CHANGED_PKGS=$(printf '%s\n%s' "$FILE_CHANGED_PKGS" "$dir")
             fi
           done
           FILE_CHANGED_PKGS=$(echo "$FILE_CHANGED_PKGS" | grep -v '^$' | sort -u || true)