wcc/ww: mangle imported symbols on dotted import path (#22 M1, #32)

Switch symbol mangling from the import leaf clause to the full dotted import path for directory packages; single-file imports keep package-clause mangling (isdir-gate: imported<=>directory-import). The root build unit's fn main stays bare, every other top-level decl mangles, closing #31's duplicate-main hazard by construction (#32). Both stages, byte-identical.

Single commit, not split: the bare rename (f244af3) is red on its own because it unmasks cross-module resolution gaps that do not reproduce pre-M1, so the fixes are intrinsic to making the rename correct. Included: wwstage fnret/fnparamslookupmod map import alias->path (#199b cross-module union-variant scrutinee resolved the wrong fn's union); cstage use_path prefers the referencing module's import for an ambiguous leaf alias (sha256 crypto.math vs strconv math). Tests table-driven: 989_m1mangle_run/_sym, 989_m1union_run (gate-visible per-arm exit codes + cs==ww byte-id).

cmd/wcc/ww.h

@@ -184,6 +184,10 @@ typedef enum {
 			 * curmod to NULL before a package-less file's bytes
 			 * (#16 option-B; the package-less-entry attribution fix
 			 * that replaces the withdrawn `package main` inject). */
+	TK_MODPATH,	/* `//ww:module <dotted-path>` — driver import boundary:
+			 * the following file's decls mangle on the full import
+			 * path, not the leaf `package` clause (M1 #22). Token
+			 * text carries the dotted path. */
 
 	TK_LAST		/* sentinel for tables */
 } Tkind;
@@ -214,6 +218,9 @@ struct Lex {
 	int	modreset;	/* a `//ww:module-reset` directive was seen in
 				 * the last skipped run; lexnext emits TK_MODRESET
 				 * before the next real token. */
+	const char *modpath;	/* a `//ww:module <path>` directive was seen in
+				 * the last skipped run; lexnext emits TK_MODPATH
+				 * carrying this dotted path (M1 #22). */
 };
 
 void	lexinit(Lex*, Arena*, const char *file, const char *src, u64 len);
@@ -340,7 +347,17 @@ struct Node {
 					 * decl's section in combined.ww.
 					 * NULL for nested nodes; only top-
 					 * level decls (fn/def/type/let)
-					 * carry it. */
+					 * carry it. On an N_USE node this is
+					 * the importing (owning) module. */
+	const char	*usepath;	/* M1 #22: on an N_USE node, the full
+					 * dotted IMPORT path (`encoding.utf8`)
+					 * vs the leaf alias in `str`. Drives
+					 * the path-keyed decl_mod match and the
+					 * qualified-ref codegen hint. */
+	int		imported;	/* M1 #22: decl reached through an
+					 * `//ww:module <path>` import boundary
+					 * (vs root/primary). Gates the root-only
+					 * bare-`main` rule (#32). */
 };
 
 Node	*newnode(Arena*, Nkind, Pos);
@@ -358,6 +375,10 @@ struct Parser {
 	const char *curmod;	/* most-recent `module foo;` declaration —
 				 * stamped onto each top-level decl that
 				 * follows. */
+	const char *pathmod;	/* M1 #22: active `//ww:module <path>` dotted
+				 * import path; while set, decls stamp
+				 * module=pathmod and imported=1, and the
+				 * in-file `package` clause is an assertion. */
 };
 
 void	parserinit(Parser*, Arena*, Lex*);