fix(formation): name-search returns null (not false) on adapter error

E2E harness exposed that the NV name-search adapter times out on a stale input
selector and search_name() swallowed the error and returned available=False --
i.e. it would tell customers an AVAILABLE name is taken. Now returns
available=None ('could not determine') on adapter error / unknown state, which the
API already maps to null. The NV/TX portal selectors still need a scraping fix
(separate task; e2e harness is the acceptance test) before enabling a self-serve
formation checkout. Documented full e2e results + the bugs caught (missing ERPNext
Items, entity_type case, missing /name-search route) in the readiness doc.

scripts/formation/base.py

@@ -68,7 +68,7 @@ class FilingStatus(str, Enum):
 
 @dataclass
 class NameSearchResult:
-    available: bool
+    available: bool | None  # True/False, or None when the lookup could not be completed (adapter error)
     exact_match: bool = False
     similar_names: list[str] = field(default_factory=list)
     state_code: str = ""

scripts/formation/name_search.py

@@ -40,7 +40,7 @@ async def search_name(name: str, state_code: str) -> NameSearchResult:
     code = state_code.upper()
     if code not in STATES:
         return NameSearchResult(
-            available=False,
+            available=None,
             searched_name=name,
             state_code=code,
             raw_response=f"Unknown state code: {code}",
@@ -58,8 +58,11 @@ async def search_name(name: str, state_code: str) -> NameSearchResult:
         return result
     except Exception as exc:
         LOG.error("Name search failed in %s: %s", code, exc, exc_info=True)
+        # available=None => "could not determine" (adapter error/portal change).
+        # NEVER return False here: a False would be read as "name taken" and could
+        # block a legitimate order or mislead the customer.
         return NameSearchResult(
-            available=False,
+            available=None,
             searched_name=name,
             state_code=code,
             raw_response=f"Error: {exc}",