fix(lang): the action drain is the program's; --check runs every check a build makes; a registry key named count is refused; name lookups are tables

- the function that calls every reducer (and the action queue) is written in the program's own
  file: in the first action's file it belonged to that module, depended on every module with a
  reducer, and joined a game's modules into one 69-module cycle (examples/actions/modules and a
  ludic deps case hold it); the state instances, the queue and the reducers make no deps edges
- ludicc --check / ludic build --check lower the program too and write nothing, so the code
  writer's refusals are in it: a bind to a function that is gone, an unknown name (and the checker
  now refuses fn <missing> itself); rejects bind_missing_fn, unknown_name, registry_count_key
- def R count is refused: its constant would be PREFIX_COUNT, the registry's size
- a file's module, package, trust and numbers-float are tables, and from the check on the lookups
  of functions, enums, records, globals and externs are too (tagged enums kept as a list): Maroon
  Lake's check-only build went from about 20 s to 7 s including lowering, its IR from about 2
  minutes to under 10 s; duplicate declarations are found by table, not a pair of loops
- threads.ludic's pool check gives each call a little work, so a busy machine cannot run them all
  on the caller before a worker wakes (it failed one run in three under load)

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

selfhost/frontend/modules.ludic

@@ -128,15 +128,9 @@ function pkg_name_of(rel: pointer) -> pointer {
 function pkg_file_set(f: pointer, name: pointer) -> void {
   push(g_pk_file, f)
   push(g_pk_name, name)
+  fm_put(g_fm_pkg, f, name)
 }
-function pkg_of_file(f: pointer) -> pointer {
-  var i = len(g_pk_file) - 1
-  while i >= 0 {
-    if (g_pk_file[i] == f) { return g_pk_name[i] }
-    i -= 1
-  }
-  return ""
-}
+function pkg_of_file(f: pointer) -> pointer { return fm_get(g_fm_pkg, f) }
 # the module a declaration is in, for the uses rule: its own, else its package's
 function module_for_uses(f: pointer) -> pointer {
   let m = module_of(f)