fix(machine): make the dispenser optional, as the validator already was

initializeHal created and initialised the dispenser unconditionally, so a
missing dispenser device threw and aborted the WHOLE of HAL init — taking
the validator down with it, even when the validator was present and
working.

The Pi bring-up hit exactly that. With a Pyramid Apex correctly wired and
enumerated on /dev/ttyValidator0:

  [ATM] Validator device: /dev/ttyValidator0
  [ATM] Dispenser device: /dev/ttyDispenser-not-fitted
  [Electron] HAL init failed: cannot open /dev/ttyDispenser-not-fitted
  [Recovery] Reloading renderer to re-attempt initialization

and round again, forever, with a perfectly good acceptor attached.

The validator has been optional since it was written — it checks the
device exists, catches init failures, and logs "running dispenser-only".
The dispenser had no equivalent. That asymmetry was the bug, not the
placeholder device path that exposed it: a cash-in-only machine is a
legitimate configuration, and the Raspberry Pi reference build is one.

Mirrors the validator's handling exactly: existence check, try/catch,
null on failure, and a log line saying what the machine will do instead
("running cash-in only"). Three call sites then need guarding —
dispenseCash returns a clear "No dispenser fitted on this machine —
cash-out unavailable" rather than dereferencing null, setCassettes still
records the layout but skips the re-init, and cleanup uses an optional
call.

This also removes the sharp edge from the rpi4/rpi5 presets added in the
previous commit. Their dispenser block points at a path that does not
exist because DispenseType has no 'none' variant and DeviceConfig
requires the field. That is still worth fixing properly with a real
'none' variant, but the machine no longer has to care.

apps/machine/electron/hal-service.ts

@@ -87,19 +87,40 @@ export async function initializeHal(config: HalConfig): Promise<HalInstance> {
 
   const { validator: valConfig, dispenser: dispConfig } = config
 
-  // Create hardware instances
+  // Start dispenser (optional — mirrors the validator handling below).
-  const dispenser: BillDispenser = hal.createDispenser(dispConfig.type, {
+  //
-    device: dispConfig.device,
+  // A cash-in-only machine is a legitimate configuration: the Raspberry Pi
-  })
+  // reference build has a bill acceptor and no dispenser at all. This used to
+  // create and init the dispenser unconditionally, so a missing device threw
+  // and aborted the WHOLE of initializeHal — taking the validator with it,
+  // even though the validator was present and working. The Pi bring-up hit
+  // exactly that: "cannot open /dev/ttyDispenser-not-fitted", then an endless
+  // renderer-reload loop, with a perfectly good acceptor on ttyValidator0.
+  //
+  // The validator has been optional since it was written; the asymmetry was
+  // the bug.
+  let dispenser: BillDispenser | null = null
 
-  // Initialize dispenser. `dispenserInitData` is `let` because
+  // `dispenserInitData` is `let` because `setCassettes` swaps it in to re-init
-  // `setCassettes` swaps it in to re-init with a new layout (also used by
+  // with a new layout (also used by the on-error re-init path at dispenseCash).
-  // the on-error re-init path at dispenseCash).
   let dispenserInitData = {
     fiatCode: valConfig.fiatCode,
     cassettes: dispConfig.cassettes,
   }
+
+  try {
+    const fs = await import('node:fs')
+    if (dispConfig.device && fs.existsSync(dispConfig.device)) {
+      dispenser = hal.createDispenser(dispConfig.type, { device: dispConfig.device })
       await dispenser.init(dispenserInitData)
+      console.log('[HAL] Dispenser started')
+    } else {
+      console.log('[HAL] Dispenser device not found, running cash-in only')
+    }
+  } catch (err) {
+    console.warn('[HAL] Dispenser failed to start, running cash-in only:', err)
+    dispenser = null
+  }
   console.log('[HAL] Dispenser initialized')
 
   // Start validator (optional — proceed without if device is missing or fails)
@@ -251,6 +272,17 @@ export async function initializeHal(config: HalConfig): Promise<HalInstance> {
     dispenseCash: async (amounts): Promise<DispenseResult> => {
       console.log('[HAL] Dispensing:', amounts)
 
+      // Cash-in-only machine: refuse the ask rather than throwing a null
+      // dereference into the renderer's dispense path.
+      if (!dispenser) {
+        return {
+          bills: [],
+          cassettes: [],
+          dispensed: false,
+          error: 'No dispenser fitted on this machine — cash-out unavailable',
+        }
+      }
+
       // Re-initialize dispenser if it was closed after a previous error
       if (!dispenser.initialized) {
         console.log('[HAL] Dispenser not initialized, re-initializing...')
@@ -391,6 +423,12 @@ export async function initializeHal(config: HalConfig): Promise<HalInstance> {
           count: c.count ?? 0,
         }))
       dispenserInitData = { fiatCode: valConfig.fiatCode, cassettes }
+      // Without a dispenser the layout is still worth recording (the operator
+      // config consumer keeps calling this), but there is nothing to re-init.
+      if (!dispenser) {
+        console.log('[HAL] Cassettes recorded; no dispenser fitted, nothing to re-init')
+        return
+      }
       // Close + re-init the dispenser so its internal per-bay state matches
       // the new layout. Errors here surface to the caller (operator-config
       // consumer) — the renderer can decide whether to retry.
@@ -407,7 +445,7 @@ export async function initializeHal(config: HalConfig): Promise<HalInstance> {
       return new Promise<void>((resolve) => {
         validator?.disable()
         validator?.lightOff()
-        dispenser.close()
+        dispenser?.close()
         if (validator) {
           validator.close((err?: Error) => {
             if (err) console.error('[HAL] Validator close error:', err)