refactor: rename host-static-{statics,objects}.ss for clarity (jolt-wn0u)

The trio split on a fine axis (registry core / statics / object classes) but the
names didn't say so — 'static-statics'/'static-objects' and headers that read
'Continues X'. Rename:
  host-static-statics.ss -> host-static-methods.ss  (Class/member statics + fields)
  host-static-objects.ss -> host-static-classes.ss  (instantiable object classes)
host-static.ss stays the registry core. Headers rewritten to state each file's role
and what it covers instead of chaining. rt.ss loads + the one comment reference +
MODULES.md updated. No code moved; runtime .ss, make test green.

docs/MODULES.md

@@ -32,7 +32,8 @@ composed and where a given `.ss` fits.
   thread-local binding stack), `dynamic-vars.ss` (a few `*…*` constant defaults),
   `atoms.ss`, `multimethods.ss`.
 - **Host interop**: `host-class.ss` (class tokens + method dispatch),
-  `host-static*.ss` (static methods/fields + host object classes), `host-table.ss`,
+  `host-static.ss` (interop registry core) + `host-static-methods.ss` (`Class/member`
+  statics) + `host-static-classes.ss` (instantiable object classes), `host-table.ss`,
   `host-contract.ss` (the `jolt.host` seam the compiler resolves against),
   `dot-forms.ss`, `records-interop.ss`.
 - **Scalars / misc**: `regex.ss` (vendored irregex), `math.ss`, `inst-time.ss`,