feat(fpagent): show scanner availability and gate capture

Consume fpagent's fprint-device-status {available, device, captureAgentId}
in the /fingerprint wizard. Availability is tracked tri-state so an agent
that does not report it leaves capture working as before; the header tag
shows offline / no-scanner / ready, the capture panel warns, and capture is
disabled until a supported reader is attached.

Adds a vm-sandbox test for the wizard logic and the OpenSpec change
fpagent-device-availability, archived with the fingerprint-wizard spec.

tools/public/assets/fp/index.html

@@ -84,6 +84,10 @@
         <span class="hint">Two fingers are required &middot; place the finger on the scanner each scan</span>
       </div>
 
+      <cds-inline-notification v-if="scannerNotice" kind="warning" hide-close-button class="mt-1"
+                               v-bind:title="scannerNotice.title" v-bind:subtitle="scannerNotice.subtitle">
+      </cds-inline-notification>
+
       <dl class="details">
         <div><dt>Name</dt><dd>{{ staff.name }}</dd></div>
         <div><dt>Reference</dt><dd>{{ staff.reference }}</dd></div>
@@ -107,11 +111,11 @@
           <p class="meta" v-if="fingers[finger].status === 'failed'">The last attempt failed. You can try again.</p>
 
           <div class="row-gap mt-1">
-            <cds-button v-if="fingers[finger].status !== 'done'" v-bind:disabled="capturing !== null" v-on:click="capture(finger)">
+            <cds-button v-if="fingers[finger].status !== 'done'" v-bind:disabled="capturing !== null || !captureReady" v-on:click="capture(finger)">
               <svg slot="icon" width="16" height="16" viewBox="0 0 32 32" fill="currentColor" aria-hidden="true" xmlns="http://www.w3.org/2000/svg"><path d="M7,5.21a.77.77,0,0,1-.46-1.38A15.46,15.46,0,0,1,16,1c2.66,0,6.48.45,9.5,2.62a.77.77,0,0,1,.18,1.07.78.78,0,0,1-1.08.17A15,15,0,0,0,16,2.53,14,14,0,0,0,7.5,5.05.74.74,0,0,1,7,5.21Z"/><path d="M28.23,12.26a.78.78,0,0,1-.63-.33C25.87,9.49,22.78,6.24,16,6.24a14,14,0,0,0-11.63,5.7.77.77,0,0,1-1.07.17A.76.76,0,0,1,3.15,11,15.54,15.54,0,0,1,16,4.71c5.61,0,9.81,2.08,12.84,6.34a.77.77,0,0,1-.19,1.07A.79.79,0,0,1,28.23,12.26Z"/><path d="M12.28,31a.78.78,0,0,1-.72-.49.75.75,0,0,1,.44-1c4.37-1.68,7-5.12,7-9.21a2.8,2.8,0,0,0-3-3c-1.86,0-2.76,1-3,3.35a4.27,4.27,0,0,1-4.52,3.83,4.27,4.27,0,0,1-4.32-4.59A11.71,11.71,0,0,1,16,8.39a12,12,0,0,1,12,11.93,18.66,18.66,0,0,1-1.39,6.5.78.78,0,0,1-1,.41.76.76,0,0,1-.41-1,17.25,17.25,0,0,0,1.27-5.91A10.45,10.45,0,0,0,16,9.92a10.18,10.18,0,0,0-10.38,10,2.77,2.77,0,0,0,2.79,3.06,2.74,2.74,0,0,0,3-2.48c.36-3.11,1.89-4.69,4.56-4.69a4.31,4.31,0,0,1,4.52,4.56c0,4.74-3,8.72-8,10.63A.92.92,0,0,1,12.28,31Z"/><path d="M19.77,30.28a.81.81,0,0,1-.52-.2.76.76,0,0,1,0-1.08,12.63,12.63,0,0,0,3.54-8.68c0-1.56-.48-6.65-6.7-6.65a6.83,6.83,0,0,0-4.94,1.87A6.17,6.17,0,0,0,9.32,20a.77.77,0,0,1-.77.76h0A.76.76,0,0,1,7.78,20,7.73,7.73,0,0,1,10,14.46a8.34,8.34,0,0,1,6-2.32c6.08,0,8.24,4.4,8.24,8.18A14.09,14.09,0,0,1,20.34,30,.75.75,0,0,1,19.77,30.28Z"/><path d="M8.66,27.74a14.14,14.14,0,0,1-1.56-.09.76.76,0,1,1,.17-1.52c2.49.28,4.45-.16,5.84-1.32a6.37,6.37,0,0,0,2.12-4.53.75.75,0,0,1,.82-.71.78.78,0,0,1,.72.81A7.89,7.89,0,0,1,14.09,26,8.2,8.2,0,0,1,8.66,27.74Z"/></svg>
               {{ fingers[finger].status === 'failed' ? 'Retry capture' : 'Capture fingerprint' }}
             </cds-button>
-            <cds-button kind="secondary" v-if="fingers[finger].status === 'done'" v-bind:disabled="capturing !== null" v-on:click="capture(finger)">
+            <cds-button kind="secondary" v-if="fingers[finger].status === 'done'" v-bind:disabled="capturing !== null || !captureReady" v-on:click="capture(finger)">
               <svg slot="icon" width="16" height="16" viewBox="0 0 32 32" fill="currentColor" aria-hidden="true" xmlns="http://www.w3.org/2000/svg"><path d="M12 10H6.78A11 11 0 0127 16h2A13 13 0 006 7.68V4H4v8h8zM20 22h5.22A11 11 0 015 16H3a13 13 0 0023 8.32V28h2V20H20z"/></svg>
               Recapture
             </cds-button>