selfhost: migrate tool sources to directory packages

Build w6a and w6l from package-main directories and expose the wcc backend through a narrow package API so w6c and wwdump no longer import implementation files. Retarget the remaining load-bearing fixtures and example sources to directory packages; retain the one intentional flat compiler collision as an explicitly composed raw unit.

selfhost/cmd/wcc/api.ww

@@ -0,0 +1,40 @@
+package wcc;
+
+import syntax;
+
+export fn compilefile(file: *syntax.node, testmode: i32, testmodule: str,
+	sepmode: i32, wwiout: str) i32 = {
+	let tc: syntax.tctx;
+	syntax.typesinit(&tc);
+	let ck: checker;
+	checkinit(&ck, &tc);
+	ck.istest = testmode;
+	if (testmodule.len > 0) { ck.testmodule = testmodule; };
+	ck.sepmode = sepmode;
+	checkfile(&ck, file);
+	if (ck.errs > 0) { return 1; };
+	if (wwiout.len > 0) {
+		if (wwiemit(&ck, file, wwiout) != 0) { return 1; };
+	};
+
+	let cg: cgen;
+	cgeninit(&cg);
+	cg.sepmode = sepmode;
+	if (wwiout.len > 0) { cg.sepisdep = 1i32; };
+	cgfile(&cg, file);
+	return 0;
+};
+
+export fn resolvefile(file: *syntax.node, verbose: i32,
+	nresolved: *i32, nunresolved: *i32) i32 = {
+	let tc: syntax.tctx;
+	syntax.typesinit(&tc);
+	let ck: checker;
+	checkinit(&ck, &tc);
+	ck.verbose = verbose;
+	checkfile(&ck, file);
+	*nresolved = ck.nresolved;
+	*nunresolved = ck.nunresolved;
+	if (ck.errs > 0 || ck.nunresolved > 0) { return 1; };
+	return 0;
+};