go: port command loop, save/restore, tcell terminal, and the binary

- command.c in full: the command dispatcher with repeat counts, run
  prefixes, ctrl-run door-stop mode, fight-to-death targeting, and all
  wizard debug commands; search, help, identify, d_level/u_level, call,
  current
- main.c completed: Run()/playit() with the C double ROGUEOPTS parse;
  exit()-anywhere becomes a gameEnd panic recovered in Run
- save.c + state.c: gob SaveState snapshot with explicit pointer-to-
  index fixups for equipment, monster rooms, and chase targets (the
  rs_fix_thing role); save file deleted on restore as in C; SIGHUP/
  SIGTERM autosave hook
- wizard.c completed (create_obj, show_map), passages.c add_pass
- term/: tcell/v2 Terminal — the one third-party dependency — replacing
  curses and mdport's 900-line key decoder; shell escape via suspend
- cmd/rogue: flags -s/-d, SEED (wizard), ROGUEOPTS, ROGUE_WIZARD

Tests: full scripted sessions through Run (quit, descend stairs,
3200-move crash sweep, save-command round trip). Notable fixes found
by tests: gob silently drops embedded fields of unexported types, and
--More-- prompts swallow space-free input scripts.

game/screen.go

@@ -138,6 +138,35 @@ func (w *Window) CopyFrom(src *Window) {
 	copy(w.cells, src.cells)
 }
 
+// Size reports the window dimensions.
+func (w *Window) Size() (rows, cols int) { return w.rows, w.cols }
+
+// CellAt reports the character and standout attribute at a position; used
+// by Terminal implementations to render the window.
+func (w *Window) CellAt(y, x int) (ch byte, standout bool) {
+	c := w.at(y, x)
+	return c.ch, c.standout
+}
+
+// Contents dumps the window characters row-major (the save file keeps the
+// visible map, as the C game saved the curses screen).
+func (w *Window) Contents() []byte {
+	out := make([]byte, len(w.cells))
+	for i, c := range w.cells {
+		out[i] = c.ch
+	}
+	return out
+}
+
+// SetContents restores a Contents dump.
+func (w *Window) SetContents(data []byte) {
+	for i := range w.cells {
+		if i < len(data) {
+			w.cells[i] = cell{ch: data[i]}
+		}
+	}
+}
+
 // Line returns row y as a trimmed string; used by tests and the death/
 // victory screens.
 func (w *Window) Line(y int) string {