w6c: fold dot chains through inferred-alloc struct pointers (#24 residue)

wwstage dotchainresolve gated its *T roots on an N_TPTR-over-N_TNAME
tnode; an inferred `let p = alloc(S{...})!` rides the checker-
SYNTHESIZED N_TPTR whose pointee is the struct BODY node (the #24
TNAME-normalize covers only the direct struct-lit binding), so the
root gate failed and chained p.field.pseudo reads fell to the
unfused deref arms — shape-only divergence vs cstage's type-keyed
fold (both stages runtime-correct; the historical field(SB) leak the
pin described was already fixed). Widen the local and global root
gates to accept the N_TSTRUCT pointee; correctness stays enforced by
the stamped-tinfo peel below (TY_PTR -> pointee TY_STRUCT).

Graduates alias_g73_heapfill out of DATABYTEID_DIVERGED (2 pins
remain, both the tagged-spill family); adds compile fixtures pinning
the newly-converged siblings (nested read+store, slice .cap,
inferred-global root; pin 1730/22/3460) and a runtime lang row that
mutates then re-points the heap base — a read bypassing the pointer
returns the wrong len.

internal/wwfixture/types.ww

@@ -1,13 +1,13 @@
 package wwfixture;
 
 def protocolversion: i32 = 1;
-def corpuscount: i32 = 1727;
+def corpuscount: i32 = 1730;
 def errorcount: i32 = 343;
-def compilecount: i32 = 19;
+def compilecount: i32 = 22;
 def runcount: i32 = 209;
 def runexitcount: i32 = 1156;
-def nativecount: i32 = 3454;
-def corpushash: str = "40ad5fd79515a743f2adb53e4a26396c6f13859df956fa079299a4b459594177";
+def nativecount: i32 = 3460;
+def corpushash: str = "5c20c19b826359fcceb45c8db5cf405f39183a68783582eaaf5f38f0e88f3771";
 
 type directive = enum i32 {
 	ERROR = 0,