Cross-validate item appearance tables against the C reference

Instrumented the C game on modern-rogue with a DUMP mode (patch in
testdata/c_seedcompat.patch) that forces the RNG seed and prints the
per-seed item appearance tables — potion colors, scroll names, ring
stones, wand/staff materials — in the normal init order, before initscr
so no terminal is needed. Captured its output for four seeds as
testdata/item_tables.golden.

TestSeedCompatItemTables regenerates the same tables from the Go port
via New(Params{Seed, Wizard: true}) and checks they match the golden
byte for byte. They do, for all four seeds — proving the LCG and its
consumption order through the whole init sequence (init_probs →
init_player → init_names → init_colors → init_stones → init_materials,
including init_player's arrow rnd(8)+rnd(15)) agree with C exactly.

testdata/README.md documents how to regenerate the golden.

game/testdata/c_seedcompat.patch

@@ -0,0 +1,37 @@
+--- a/main.c	2026-07-24 03:02:38
++++ b/main.c	2026-07-24 02:48:31
+@@ -63,6 +63,34 @@
+ #endif
+ 	dnum = lowtime + md_getpid();
+     seed = dnum;
++
++    /* SEEDCOMPAT: dump the per-game item appearance tables for a fixed
++     * seed and exit, without initscr. The init sequence and everything
++     * it consumes from rnd() mirror the normal startup (main.c), so the
++     * tables are exactly what a real game with SEED would show. */
++    if (getenv("DUMP") != NULL)
++    {
++	int di;
++	char *sv = getenv("SEED");
++	if (sv != NULL)
++	    seed = atoi(sv);
++	printf("SEED %d\n", seed);
++	init_probs();
++	init_player();
++	init_names();
++	init_colors();
++	init_stones();
++	init_materials();
++	printf("POTIONS\n");
++	for (di = 0; di < MAXPOTIONS; di++) printf("%s\n", p_colors[di]);
++	printf("SCROLLS\n");
++	for (di = 0; di < MAXSCROLLS; di++) printf("%s\n", s_names[di]);
++	printf("RINGS\n");
++	for (di = 0; di < MAXRINGS; di++) printf("%s\n", r_stones[di]);
++	printf("STICKS\n");
++	for (di = 0; di < MAXSTICKS; di++) printf("%s %s\n", ws_type[di], ws_made[di]);
++	exit(0);
++    }
+ 
+     open_score();
+