w6c: 'as' on a module-global tagged ident loads the full box

cstage's N_TYPEASSERT assumed cgexpr filled the registers and spilled
an uninitialized payload (cs=0 for any stored value); mirror the
landed wwstage emission (tag/payload/cap from g(SB)). Flips the
residual row to cs==ww==correct. Task #46.

test/wcc/989_globtagisas_run.c

@@ -14,24 +14,21 @@
  *  • `is` half = ALIGN-UP. cstage reads the tag correctly (MOVQ g(SB),AX);
  *    wwstage read 0(BP). FIX routes the global ident to MOVQ g(SB),AX →
  *    cs==ww + runtime-correct (the is_* rows assert want on BOTH drivers).
- *  • `as` half = #263 BOTH-WRONG. cstage N_TYPEASSERT on a global ident also
- *    fails: it spills cgexpr's AX (tag only) plus UNINITIALIZED DX as the
- *    payload (never loads g(SB)+8) → returns garbage (0). The wwstage FIX
- *    copies the global box words from g(SB)+0/+8[/+16] into a fresh
- *    @asrt_spill so the tag-check + payload load index off memory like a
- *    local → ww runtime-correct, while cstage stays wrong: cs≠ww residual
- *    BY DESIGN until the cstage half lands (ww-core TASK #46). The as_* rows
- *    assert ww-correct AND pin cstage's documented-wrong value so the residual
- *    is never misread as a regression.
+ *  • `as` half = #263 BOTH-WRONG, now CLOSED both stages. cstage N_TYPEASSERT
+ *    on a global ident spilled cgexpr's AX (tag only) plus UNINITIALIZED DX as
+ *    the payload (never loaded g(SB)+8) → garbage (0). The ww half landed in
+ *    F8-c3; the cstage half (copy the box words from g(SB)+0/+8[/+16] into the
+ *    @asrt_spill so the tag-check + payload load index off memory like a local)
+ *    landed in ww-core TASK #46. Both stages now read the real payload and the
+ *    .s is byte-identical.
  *
- * Rows (built+run on cstage `ww` and wwstage `ww_ww`; each driver checked
- * against ITS expected — want_cs / want_ww — to encode the #263 residual):
- *   row       | shape                                  | cs | ww | cat
- *   ----------+----------------------------------------+----+----+--------
- *   is_match  | g:(i64|bool)=5; if g is i64 →0 else 12   | 0  | 0  | align-UP
- *   is_nomatch| g:(i64|bool)=5; if g is bool →13 else 0  | 0  | 0  | align-UP
- *   as_i64    | g:(i64|bool)=42; (g as i64):int          | 0  | 42 | #263 (#46)
- *   as_str    | g:(str|i64)="hello"; len(g as str)       | 0  | 5  | #263 (#46)
+ * Rows (built+run on cstage `ww` and wwstage `ww_ww`; cs==ww on every row):
+ *   row       | shape                                  | exit | cat
+ *   ----------+----------------------------------------+------+--------
+ *   is_match  | g:(i64|bool)=5; if g is i64 →0 else 12   | 0   | align-UP
+ *   is_nomatch| g:(i64|bool)=5; if g is bool →13 else 0  | 0   | align-UP
+ *   as_i64    | g:(i64|bool)=42; (g as i64):int          | 42  | #46
+ *   as_str    | g:(str|i64)="hello"; len(g as str)       | 5   | #46
  */
 #include <stdio.h>
 #include <stdlib.h>
@@ -71,22 +68,22 @@ static const struct row rows[] = {
 	  "export fn main() int = { return check(); };\n",
 	  0, 0 },
 
-	/* #263: cstage spills uninitialized DX as the payload (task #46) →
-	 * returns 0; wwstage copies the box from g(SB) → 42. */
+	/* #46 CLOSED both stages: cstage now copies the box from g(SB) into the
+	 * @asrt_spill (was spilling uninitialized DX) → 42 == wwstage. */
 	{ "as_i64",
 	  "package main;\n"
 	  "let g: (i64 | bool) = 42;\n"
 	  "fn check() int = { let x: i64 = g as i64; return x: int; };\n"
 	  "export fn main() int = { return check(); };\n",
-	  0, 42 },
+	  42, 42 },
 
-	/* #263: str variant — wwstage copies the +16 cap word too (task #46). */
+	/* #46 str variant — both stages copy the +16 cap word too. */
 	{ "as_str",
 	  "package main;\n"
 	  "let g: (str | i64) = \"hello\";\n"
 	  "fn check() int = { let s: str = g as str; return len(s): int; };\n"
 	  "export fn main() int = { return check(); };\n",
-	  0, 5 },
+	  5, 5 },
 };
 
 /* run_build — build+run `src` via `driver`; returns the binary's exit