fix(hal): EBDS escrow stack/return latch + return-on-disable

Cash-in stalled on the batm3: a note reached escrow and was read, but the
acceptor never stacked or returned it, and the customer was never
credited. Root cause: EBDS carries the stack/return decision as bits in
the omnibus *poll* command, but the driver sent stack()/reject() as a
single one-shot frame while a free-running 100ms poller kept sending
plain polls. The lone stack frame races/collides with the poller (or its
ack desyncs), gets dropped, and the device holds the note in escrow
indefinitely.

- ebds-rs232: latch the escrow decision (`pendingAction`) into the poll
  command byte and re-assert it on every poll until the device leaves
  escrow (cleared in _process when `!escrowed`). A dropped frame is now
  simply retried on the next poll.
- hal-service: return an escrowed note on disableValidator() — disable
  alone does not release it on EBDS, so an inactivity timeout / cancel
  previously stranded the bill in the transport (observed on the batm3).
- atm store: stringify the `[ATM] Sending event` / `[ATM] State` logs —
  they were printing `[object Object]`, which blinded the cash-in trace.

Verified: hal builds, machine app typechecks. Hardware behaviour to be
confirmed on the batm3 (no unit tests exist for this serial driver).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

packages/hal/src/validators/ebds/ebds-rs232.ts

@@ -313,6 +313,13 @@ export class EbdsRs232 extends EventEmitter {
   private serial: SerialPort | null = null
   private ack: number = 0x0
   private enabledDenominations: number = 0x00
+  // Latched escrow decision. In EBDS the stack/return choice is NOT a one-shot
+  // message — it's carried as bits in the omnibus poll command, and the device
+  // holds the escrowed note until a poll asserts stack or return. We keep the
+  // action set and re-assert it on every poll until the device leaves escrow
+  // (cleared in _process), so a single dropped/collided frame no longer strands
+  // the note in escrow forever.
+  private pendingAction: 'none' | 'stack' | 'return' = 'none'
   private lastStatusFlags: string | null = null
   private firmwareLogged: boolean = false
 
@@ -405,23 +412,38 @@ export class EbdsRs232 extends EventEmitter {
 
   // -- Commands (Appendix D, Controller Message) ---------------------------
 
-  /** Send an Omnibus poll command with current denomination mask */
+  /**
+   * Command byte 1 for the omnibus poll, encoding any latched escrow action.
+   * `stack` (0x3f) and `return` (0x5f) differ from the plain poll (0x1b) only
+   * in the stack/return bits; while an action is latched every poll re-asserts
+   * it until the device acts.
+   */
+  private commandByte(): number {
+    if (this.pendingAction === 'stack') return 0x3f
+    if (this.pendingAction === 'return') return 0x5f
+    return 0x1b
+  }
+
+  /** Send an Omnibus poll command with the current mask + latched action */
   poll(): void {
-    this._dispatch([this.enabledDenominations, 0x1b, 0x10])
+    this._dispatch([this.enabledDenominations, this.commandByte(), 0x10])
   }
 
-  /** Stack the bill currently in escrow */
+  /** Latch "stack the escrowed note"; re-asserted each poll until it takes. */
   stack(): void {
-    this._dispatch([this.enabledDenominations, 0x3f, 0x10])
+    this.pendingAction = 'stack'
+    this.poll()
   }
 
-  /** Reject/return the bill currently in escrow */
+  /** Latch "return the escrowed note"; re-asserted each poll until it takes. */
   reject(): void {
-    this._dispatch([this.enabledDenominations, 0x5f, 0x10])
+    this.pendingAction = 'return'
+    this.poll()
   }
 
   /** Send initial setup command (disable all, reset state) */
   reset(): void {
+    this.pendingAction = 'none'
     this._dispatch([0x00, 0x1b, 0x10])
   }
 
@@ -470,7 +492,13 @@ export class EbdsRs232 extends EventEmitter {
       validatePacket(packet)
       const result = interpret(packet)
       if (result) {
-        if (result.destructedData) this._logStatusOnChange(result.destructedData)
+        if (result.destructedData) {
+          // Clear a latched stack/return once the device has left escrow — it
+          // is now stacking/returning/idle, so we must stop asserting the
+          // action or it would leak onto the next note.
+          if (!result.destructedData[0].escrowed) this.pendingAction = 'none'
+          this._logStatusOnChange(result.destructedData)
+        }
         this.emit('message', result)
       }
     } catch (ex) {