lib/ww/ast: nkname if-ladder -> switch (Wave-2 structural)

Fold the 69-arm `if (k == nkind.N_X) return "..."` ladder in nkname to a
single `switch (k)` with the terminal `return "?"` as the fall-past
default. The other ast.ww ladders stay: pr()'s kind dispatch is
side-effecting (emits output, recurses) and uses ||-grouped multi-kind
predicates, not a pure value->value mapping a switch can express.

Not byte-id-neutral (if-chain -> switch dispatch changes the asm), so
the ladder->switch equivalence is pinned by a new table-driven test:
lib/ww/asttest.ww drives nkname over every nkind plus the out-of-band
"?" fallback, wired as 905_nkname_run (same `ww run` @test shape as
904_tok_run). The 990_selfhost wwdump diff only covers kinds that
appear in its corpus.

Regenerates the w6c + wwdump combined.ww amalgamations (nkname region
only).

test/wcc/905_nkname_run.c

@@ -0,0 +1,57 @@
+/*
+ * 905_nkname_run — execute the lib/ww nkname @test fixture under the
+ * C-side `ww run` driver and assert exit 0.
+ *
+ * Same thin-wrapper shape as 904_tok_run / 904_ascii_run: asttest.ww
+ * carries its own `export fn main()` that drives the @test fn and
+ * signals which case failed via the exit code. This pins nkname's
+ * if-ladder -> switch fold (every nkind + the unknown-kind fallback),
+ * which the 990_selfhost wwdump diff only covers for kinds that appear
+ * in its corpus.
+ *
+ * Unlike 904_tok_run, the fixture imports `ast` (package ww), whose
+ * printer references tok's tkind/tokname, so the run needs
+ * `-I lib/ww/lex` to resolve that transitive import.
+ */
+#include <stdio.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <sys/wait.h>
+
+static int
+runwait(const char *cmd)
+{
+	int rc = system(cmd);
+	if (rc == -1) return -1;
+	if (WIFEXITED(rc)) return WEXITSTATUS(rc);
+	return 1;
+}
+
+int
+main(void)
+{
+	const char *bin = getenv("BIN");
+	if (!bin) bin = "out/bin";
+	char absbin[1024];
+	if (bin[0] != '/') {
+		char cwd[1024];
+		if (getcwd(cwd, sizeof cwd) == NULL) return 1;
+		snprintf(absbin, sizeof absbin, "%s/%s", cwd, bin);
+		bin = absbin;
+	}
+	char cwd[1024];
+	if (getcwd(cwd, sizeof cwd) == NULL) return 1;
+
+	const char *src = "lib/ww/asttest.ww";
+	char path[1024], inc[1024], cmd[3072];
+	snprintf(path, sizeof path, "%s/%s", cwd, src);
+	snprintf(inc, sizeof inc, "%s/lib/ww/lex", cwd);
+	snprintf(cmd, sizeof cmd, "%s/ww run -I %s %s", bin, inc, path);
+	int rc = runwait(cmd);
+	if (rc != 0) {
+		fprintf(stderr, "nkname_run FAIL: %s exited %d\n", src, rc);
+		return 1;
+	}
+	printf("nkname_run: %s ok\n", src);
+	return 0;
+}