fix(search): soft-fail on per-row excluded type and malformed regex name

Cross-task review found two edge cases that violated the basket-mode
soft-fail contract:

- Per-row excluded type (e.g. type = c(NA, "special_district")) hit
  .coerce_type()'s abort inside the per-row resolver, killing the
  whole basket call. Now treated as no_match in the sidecar.
- Malformed regex in the substring fallback (e.g. name = "San(Diego")
  propagated DuckDB engine errors. .escape_regex() now backslash-
  escapes meta characters before the regexp_matches call. Utility-
  mode regex behavior is unchanged.

Plus a new public-surface test for the all-no-match case.

R/basket.R

@@ -39,9 +39,12 @@
 }
 
 # Convert a type input (integer-like or label) into the canonical label
-# string used in the sidecar query_type column.
+# string used in the sidecar query_type column. Excluded types (4/5 /
+# special_district / school_district) are returned as-is so the sidecar
+# records what the user passed without calling .coerce_type() (which aborts).
 #' @noRd
 .type_to_label <- function(type) {
+  if (.is_excluded_type(type)) return(as.character(type))
   int_type <- .coerce_type(type)
   unname(c("0" = "state", "1" = "county", "2" = "city", "3" = "township")[[as.character(int_type)]])
 }