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/command_test.go

@@ -0,0 +1,37 @@
+//nolint:testpackage // white-box tests reach unexported state (approved 2026-07-07)
+package game
+
+import "testing"
+
+// TestRedrawCommandForcesFullRepaint pins CTRL-R to a forced repaint
+// rather than an ordinary refresh. C's arm is "after = FALSE;
+// clearok(curscr, TRUE); wrefresh(curscr);" (command.c), and the
+// clearok is the command: a diffing refresh compares the new frame
+// against the device's record of the old one and sends nothing when they
+// agree, which is exactly the situation after some other program has
+// scribbled on the terminal. Only the terminal can tell the difference,
+// so the test watches the terminal rather than the window contents.
+func TestRedrawCommandForcesFullRepaint(t *testing.T) {
+	t.Parallel()
+
+	g := mkGameInput(t)
+
+	term, ok := g.scr.term.(*testTerm)
+	if !ok {
+		t.Fatal("game terminal is not a testTerm")
+	}
+
+	before := term.repaints
+	g.After = true
+
+	g.dispatch(CTRL('R'))
+
+	if term.repaints != before+1 {
+		t.Errorf("terminal repainted %d times, want %d: CTRL-R did not force "+
+			"a full redraw", term.repaints-before, 1)
+	}
+
+	if g.After {
+		t.Error("CTRL-R consumed a turn; C sets after = FALSE")
+	}
+}