test/wcc/data: pin the drained divergences at runtime

The four graduated pin families byte-compared under test-data-byteid
but their original fixtures masked the miscompiles at runtime (lone
frame slot, dead code path, pointer accident). Add the discriminating
programs as run fixtures: adjacent-element clobber for the 2-byte
deref store, second-variant match dispatch for fn-type dedup, payload
integrity across the tagged widen of a padded struct, and base64
clear() actually zeroing its buffers. Corpus pins move to 1,229
fixtures / 137 run / 766 run-exit / 2,458 cells with the new identity
hash; the data-byteid floor moves to 915.

internal/wwfixture/types.ww

@@ -1,13 +1,13 @@
 package wwfixture;
 
 def protocolversion: i32 = 1;
-def corpuscount: i32 = 1225;
+def corpuscount: i32 = 1229;
 def errorcount: i32 = 314;
 def compilecount: i32 = 12;
-def runcount: i32 = 136;
-def runexitcount: i32 = 763;
-def nativecount: i32 = 2450;
-def corpushash: str = "a2e47b2967d51a517d39598caf69c2d23618ba488594a0b7e33fded27cc62f93";
+def runcount: i32 = 137;
+def runexitcount: i32 = 766;
+def nativecount: i32 = 2458;
+def corpushash: str = "9d1db4b4bdde1b7e2b1f2e2ae5ca6c6b91b0162df585fd877021d27ec6863d89";
 
 type directive = enum i32 {
 	ERROR = 0,