wwi: derive decl-less module's .wwi package leaf from parse-stamped path (#11)

wwi_emit took the .wwi `package` leaf from the first primary decl's module tag;
a fully empty primary module body (zero decls) had none, so the leaf stayed the
literal default "main" and the importer rejected it ("package main does not
match import path <leaf>"). The module identity is only available at parse time
(curmod is overwritten by imported //ww:module sections before emit), so stamp
the primary path onto the N_FILE node (TK_MODULE and TK_MODRESET rp!=NULL sites,
only-if-empty so a bare-reset `package main` root stays "main") and, when the
decl-scan finds no leaf, fall back to that stamped path. Symmetric cstage+
selfhost; both detect scan-miss via the same found-flag so the emitted .wwi
stays byte-identical.

Regression: test/wcc/989_wwileaf_run.c, table-driven over {empty body,
comment-only, nested a.b.c} decl-less shapes, non-vacuity proven.

cmd/wcc/parse.c

@@ -1442,6 +1442,13 @@ parsefile(Parser *p)
 				}
 			} else {
 				p->curmod = name;
+				/* #11: stamp the primary module identity on the
+				 * N_FILE node so wwi_emit can derive the
+				 * `package` leaf even when the body carries zero
+				 * module-tagged decls. Primary identity only;
+				 * never the imported boundary (TK_MODPATH). */
+				if (file->module == NULL)
+					file->module = name;
 			}
 			continue;
 		}
@@ -1478,6 +1485,13 @@ parsefile(Parser *p)
 			if (rp != NULL) {
 				p->curmod = rp;
 				p->resetmod = rp;
+				/* #11: path-carrying reset is a primary body
+				 * identity (sep); stamp it for the wwi leaf
+				 * fallback. A bare reset (rp==NULL) is the
+				 * root/package-less boundary and MUST keep the
+				 * "main" default — so do NOT stamp there. */
+				if (file->module == NULL)
+					file->module = rp;
 			} else {
 				p->curmod = NULL;
 				p->resetmod = NULL;