check: populate fn-type params in the wwstage tinfo layer

The N_TFN arm stamped only size and return, so every fn tinfo carried
a nil param chain and typeeq judged any two same-return fn types
equal: tagged-union dedup collapsed (*fn(A) T | *fn(B) T) to a bare
8-byte pointer and match read the pointer word as a tag, falling
through every arm for a real second-variant value. Build the tparam
chain like cstage's N_TFN resolve (bare ... sets the FFI variadic
flag; a Hare T... param wraps to []T with a per-param variadic bit
that typeeq now compares, mirroring cstage type_eq). Graduates the
four r76_typeeq_fn pins; the DATABYTEID_DIVERGED ledger is empty.

Makefile

@@ -581,10 +581,9 @@ DATABYTEID_EXPECTED_MIN = 911
 # Known cs!=ww divergences (loud over blind, the 989_lib_byteid DIVERGE
 # discipline): each entry must still build on both stages AND still differ.
 # When a compiler fix lands the entry fails demanding graduation out of
-# this list rather than silently widening coverage.  Tracked with the #59
-# divergence family.
-DATABYTEID_DIVERGED = r76_typeeq_fn_diff_arity r76_typeeq_fn_diff_param_type \
-	  r76_typeeq_fn_io_vtable_shape r76_typeeq_fn_variadic_vs_fixed
+# this list rather than silently widening coverage.  Currently empty: the
+# 2026-08 drain closed all eight original entries.
+DATABYTEID_DIVERGED =
 $(if $(DATABYTEID_FILES),,$(error test-byteid: empty data corpus))
 test-data-byteid: $(BIN)/ww $(BIN)/w6c $(BIN)/w6c_ww
 	@work=$$(mktemp -d "$(CURDIR)/$(DATABYTEID_DIR).XXXXXX") || exit 1; \