test: migrate Fam11 float value tests to @test, keep ABI-conformance pins (#5-C4)

fold-2 chunk C4 (drew's Fam8-13 plan): 13 float value-row C drivers re-homed.
11 migrate to test/lang/*_test.ww @test row-tables (exact IEEE-bit asserts);
1 float-overflow reject row -> a runww //ww:error carrier. 956_tuprecv_f64
slims to a w6c_ww asserttyped pin (20 value rows -> @test; the stamp dimension
can't be a value/byte-id @test) -- mutation-proven non-vacuous (break #121
stamp -> RED 6/6 -> restore -> GREEN) + an in-test vacuity self-check.
946_structparam/structret stay whole: their SSE register-class .s-grep (SysV
ABI conformance, #165/#171a) is the genuine defect-guard, not @test-expressible.
Float was the predicted SSE-cursor byte-id hotspot -- zero fresh cs!=ww
surfaced; 951_f64cgen (cstage-only before) byte-ids clean. LANGBYTEID floor
82->93; test count 384->374 (10 deleted drivers; 956 + the 2 946 kept).

test/wcc/data/floatlit_overflow/case.ww

@@ -0,0 +1,10 @@
+//ww:error "bad float literal"
+// 989_floatlit overflow leg: 1.7976931348623159e308 rounds above DBL_MAX —
+// cstage strtod sets ERANGE, wwstage stof64 overflows; BOTH stages must reject
+// (runww ERROR arm runs w6c AND w6c_ww). Migrated from 989_floatlit_run.c
+// fixture 2 (#5-C4).
+package main;
+export fn main() i32 = {
+	let a: f64 = 1.7976931348623159e308;
+	return 0;
+};