WIP: restore lost C behaviors (schtick message, forced redraw, greeting)

Incomplete checkpoint, preserved after the implementing session hit a
capacity limit partway through mutation verification. NOT reviewed and NOT
gate-clean: make fmt has not been run, so fmt-check currently fails on
ARCHITECTURE.md and TODO.md.

Work still outstanding before this is fit for review:
  - run make fmt and fold the result in
  - finish mutation-proving each of the three behaviors
  - verify every message string byte-for-byte against the C sources
  - confirm TestSeedCompatItemTables passes with its golden untouched

Refs #13.

game/greeting_test.go

@@ -0,0 +1,64 @@
+//nolint:testpackage // white-box tests reach unexported state (approved 2026-07-07)
+package game
+
+import (
+	"strings"
+	"testing"
+)
+
+// TestGreeting pins both wordings of main.c's pre-initscr printf byte for
+// byte. The wizard one carries dnum, which main.c has just assigned to
+// seed, so it is the seed the player sees. Neither ends in a newline: C
+// printed, flushed, and handed the display to curses.
+func TestGreeting(t *testing.T) {
+	t.Parallel()
+
+	cases := []struct {
+		name   string
+		params Params
+		want   string
+	}{
+		{
+			name:   "normal",
+			params: Params{Name: "conan", Seed: 4242},
+			want:   "Hello conan, just a moment while I dig the dungeon...",
+		},
+		{
+			name:   "wizard names the dungeon",
+			params: Params{Name: "conan", Seed: 4242, Wizard: true},
+			want:   "Hello conan, welcome to dungeon #4242",
+		},
+		{
+			// parse_opts runs before the printf in main.c, and whoami
+			// falls back to the account name only when ROGUEOPTS left it
+			// empty, so the option is what the player is greeted by.
+			name: "ROGUEOPTS name wins over the account name",
+			params: Params{
+				Name: "conan", Seed: 7, RogueOpts: "name=Rodney",
+			},
+			want: "Hello Rodney, just a moment while I dig the dungeon...",
+		},
+		{
+			name: "ROGUEOPTS without a name keeps the account name",
+			params: Params{
+				Name: "conan", Seed: 7, RogueOpts: "terse,fruit=mango",
+			},
+			want: "Hello conan, just a moment while I dig the dungeon...",
+		},
+	}
+
+	for _, tc := range cases {
+		t.Run(tc.name, func(t *testing.T) {
+			t.Parallel()
+
+			got := Greeting(tc.params)
+			if got != tc.want {
+				t.Errorf("Greeting() = %q, want %q", got, tc.want)
+			}
+
+			if strings.HasSuffix(got, "\n") {
+				t.Error("greeting ends in a newline; C's printf did not")
+			}
+		})
+	}
+}