Rongta 80mm printer: driver, role-based failover, live status monitoring

Add the rongta PrinterDevice driver (ESC/POS over raw TCP 9100) and the
device-agnostic pieces around it:

- Roles + failover: each printer declares a role (entry-dispenser/booth-
  receipt) and failoverRank; printer-routing.ts picks the best healthy printer
  and falls back outside->booth for entry tickets (never the reverse).
- Live status: MonitorableDevice.readStatus()/PrinterStatus capability. The
  Rongta driver scrapes the device's own /prn_stat.htm (Cover/Cutter/Paper
  End/Near End/Off-Line) rather than hand-decoding DLE EOT, whose reply bytes
  on this clone don't match the canonical ESC/POS bit layout (verified on
  hardware) -- avoids a false-healthy. Maps to ready/degraded/offline, fail
  safe on an unreachable or unexpected page.
- Server PrinterMonitor polls enabled printers (PRINTER_POLL_MS, default 5s),
  caches latest, emits "printer-status" on change. Exposed via
  GET /api/printers/status and an SSE stream for the booth UI.

Verified against 10.0.10.6: ready when healthy, offline when unreachable
(no throw), bus emits on change and suppresses unchanged reads.

Wiki: new rongta-printer entity, printer-roles-failover and
printer-status-monitoring concepts; BOM/index/log updated.

packages/devices/src/interfaces.ts

@@ -191,3 +191,37 @@ export interface TicketData {
 export interface PrinterDevice extends Device {
   printTicket(data: TicketData): Promise<void>;
 }
+
+// --- Live printer status (consumable / mechanical faults) ----------------
+// Optional capability: a printer that reports the operator-actionable faults a
+// basic `healthCheck` (reachability) can't see — paper out, cover open, cutter
+// jam. Used by the live status monitor so the booth knows BEFORE a driver presses
+// the entry button and no ticket comes out. The Rongta board exposes these via
+// its own status web page (it decodes the ESC/POS bits for us — more reliable
+// than trusting a clone's DLE EOT bit layout). See wiki/concepts/printer-status-monitoring.md.
+export interface PrinterStatus {
+  /** Reachable + no fault = ready; reachable + fault = degraded; unreachable = offline. */
+  readonly status: "ready" | "degraded" | "offline";
+  /** Out of paper — the printer cannot print. */
+  readonly paperEnd?: boolean;
+  /** Paper low — still prints, but warn the operator to reload. */
+  readonly paperNearEnd?: boolean;
+  /** Cover/lid open — will not print. */
+  readonly coverOpen?: boolean;
+  /** Cutter jammed/errored. */
+  readonly cutterError?: boolean;
+  /** Printer reports itself off-line (its own flag, distinct from unreachable). */
+  readonly offline?: boolean;
+  /** Human-readable summary (e.g. "paper out", or the unreachable error). */
+  readonly detail?: string;
+  readonly checkedAt: string; // ISO-8601
+}
+
+export interface MonitorableDevice {
+  /** Richer, operator-actionable status beyond reachability. */
+  readStatus(): Promise<PrinterStatus>;
+}
+
+export function isMonitorable(device: Device): device is Device & MonitorableDevice {
+  return typeof (device as Partial<MonitorableDevice>).readStatus === "function";
+}