Add global-install support and document installation in README

- scripts/generate_global_tables.py generates sym-lib-table.global /
  fp-lib-table.global using a custom env var (default MIKILAB) instead
  of ${KIPRJMOD}, for use across every KiCad project
- README §1 now has concrete, tested install steps for this machine's
  KiCad 10.0 setup (per-project vs. global), including a merge script
  and a note about stale kicad-personal-library entries already
  present in the user's global sym-lib-table

scripts/check_library.py

@@ -33,7 +33,8 @@ ROOT = lc.LIBRARY_ROOT
 
 EXPECTED_TOP_LEVEL = {
     "symbols", "footprints", "3dmodels", "docs", "legacy", "scripts",
-    "sym-lib-table", "fp-lib-table", "MANIFEST.csv", "MANIFEST.md",
+    "sym-lib-table", "fp-lib-table", "sym-lib-table.global", "fp-lib-table.global",
+    "MANIFEST.csv", "MANIFEST.md",
     "README.md", ".git", ".claude", ".gitignore", ".DS_Store",
 }