wcc: dot-lhs prefers SK_USE module over same-leaf type/fn name

The wwstage checker resolved a module-qualified call/access mod.x by the
same-module preference in scopelookupprefer, so when the importing package's
name collides with a type/fn of the same leaf (package fnmatch with fn fnmatch;
package random with type random), the dot-lhs mod resolved to the same-leaf
SK_TYPE/SK_FN instead of the coexisting SK_USE import — the N_DOT module-qual
arm never fired and the call went nil-stamped (the D class of the asserttyped
gap audit: fnmatch 2, random 16). cstage resolves this via Sym.use_alias; this
ports the equivalent to wwstage.

Add scopelookupuselocal (a single-scope SK_USE lookup, twin of scopelookuptype)
and prefer SK_USE for a dot-lhs in exprtype's N_CALL and N_DOT arms, keyed on
the scope where scopelookupprefer landed so a local binding sharing a module's
leaf keeps value semantics. Scope-layer only — no type-identity touch (cstage
use_alias never reaches type_eq).

Drives the 901 gap-corpus D count to 0 (random_test now byte-id cs==ww).
Compiler binary unchanged (no such collision in its own source); 990-997 hold.
The separate fnmatch bare-enum-member cgen cs!=ww is unrelated (filed).

test/wcc/901_asserttyped_gap.c

@@ -23,8 +23,8 @@
  *   A  module-qual N_DOT call result   checked_test   0  (closed)
  *   B  fn-ptr struct-field call         smoke          3
  *   C  abort intrinsic callee           utf8           8
- *   D  module-leaf == type/fn name      fnmatch        2
- *   D  module-leaf == type/fn name      random        16
+ *   D  module-leaf == type/fn name      fnmatch        0  (closed)
+ *   D  module-leaf == type/fn name      random         0  (closed)
  *
  * Exit code of wwdump_ww is intentionally not gated: the diagnostics
  * land on stderr regardless of the run's success, and arming the bail
@@ -113,9 +113,9 @@ main(void)
 		{ "lib/encoding/utf8/utf8.combined.ww",
 		  "C abort intrinsic callee", 8 },
 		{ "lib/fnmatch/fnmatchtest.combined.ww",
-		  "D module-leaf == type/fn name", 2 },
+		  "D module-leaf == type/fn name", 0 },
 		{ "lib/math/random/random_test.combined.ww",
-		  "D module-leaf == type/fn name", 16 },
+		  "D module-leaf == type/fn name", 0 },
 		{ NULL, NULL, 0 },
 	};
 
@@ -151,6 +151,6 @@ main(void)
 		return 1;
 	}
 	printf("asserttyped_gap: ww-stage checker warn set matches manifest "
-	    "on %d gap-corpus fixtures (B+C+D pinned, A closed)\n", n);
+	    "on %d gap-corpus fixtures (B+C pinned, A+D closed)\n", n);
 	return 0;
 }