refactor(tui): /clean pass on tui-polish — data tables, tighter title

- normalizeStatusBar: replace Set + early-returns + cast with a single
  alias lookup table. Handles legacy `false`, trims/lowercases strings,
  maps `on` → `top` in one pass. One expression, no `as` hacks.
- Tab title block: drop the narrative comment, fold
  blockedOnInput/titleStatus/cwdTag/terminalTitle into inline expressions
  inside useTerminalTitle. Avoids shadowing the outer `cwd`.
- tui_gateway statusbar set branch: read `display` once instead of
  `cfg0.get("display")` twice.

tui_gateway/server.py

@@ -2528,8 +2528,8 @@ def _(rid, params: dict) -> dict:
 
     if key == "statusbar":
         raw = str(value or "").strip().lower()
-        cfg0 = _load_cfg()
-        d0 = cfg0.get("display") if isinstance(cfg0.get("display"), dict) else {}
+        display = _load_cfg().get("display")
+        d0 = display if isinstance(display, dict) else {}
         current = _coerce_statusbar(d0.get("tui_statusbar", "top"))
 
         if raw in ("", "toggle"):