Stream slave accel via ESP-NOW with master snapshot cache.

Slaves push BMA456 samples at 16ms when enabled; the master caches per
client and exposes ACCEL_SNAPSHOT and ACCEL_STREAM over UART. goTool adds
dashboard stream controls, HTTP accel-stream routes, and an external
WebSocket API with per-connection receive/interval and slave stream commands.

Co-authored-by: Cursor <cursoragent@cursor.com>

goTool/webui/index.html

@@ -55,11 +55,12 @@
     .badge-offline { background: #5c6570; color: #f0f3f5; }
     .badge.bg-secondary { background: #4a5560 !important; color: #f0f3f5; }
 
-    .mac {
+    .mac, .accel {
       font-family: ui-monospace, monospace;
       font-size: 0.85rem;
       color: var(--pp-accent);
     }
+    .accel-stale { color: var(--pp-text-muted); }
 
     .pp-table {
       --bs-table-color: var(--pp-text);
@@ -265,7 +266,9 @@
               <span class="badge bg-secondary" x-text="(state.clients || []).length + ' registered'"></span>
             </div>
           </div>
-          <p class="text-muted small px-3 pt-2 mb-0">Slaves per ESP-NOW — Master-Deadzone bleibt separat.</p>
+          <p class="text-muted small px-3 pt-2 mb-0">
+            Accel-Stream pro Slave per „Stream an“ aktivieren (~16&nbsp;ms ESP-NOW). Ohne Aktivierung keine Werte.
+          </p>
           <div class="card-body p-0 pt-2">
             <div class="table-responsive">
               <table class="table pp-table table-hover">
@@ -276,12 +279,14 @@
                     <th>Ver</th>
                     <th>Status</th>
                     <th>Deadzone</th>
+                    <th>Accel (LSB)</th>
+                    <th>Stream</th>
                     <th>Aktion</th>
                   </tr>
                 </thead>
                 <tbody>
                   <template x-if="!(state.clients || []).length">
-                    <tr><td colspan="6" class="text-muted text-center py-4">No clients</td></tr>
+                    <tr><td colspan="8" class="text-muted text-center py-4">No clients</td></tr>
                   </template>
                   <template x-for="c in (state.clients || [])" :key="c.id + c.mac">
                     <tr>
@@ -294,6 +299,20 @@
                               x-text="c.available ? 'available' : 'inactive'"></span>
                       </td>
                       <td x-text="c.deadzone != null ? c.deadzone : '—'"></td>
+                      <td>
+                        <span class="accel"
+                              :class="accelCellClass(c)"
+                              x-text="formatAccel(c)"
+                              :title="accelTitle(c)"></span>
+                      </td>
+                      <td>
+                        <button type="button"
+                                class="btn btn-sm"
+                                :class="c.accel_stream ? 'btn-warning' : 'btn-outline-success'"
+                                @click="setAccelStream(c.id, !c.accel_stream)"
+                                :disabled="busy || !state.uart_connected || !c.available"
+                                x-text="c.accel_stream ? 'Aus' : 'An'"></button>
+                      </td>
                       <td>
                         <div class="d-flex flex-wrap gap-1 align-items-center">
                           <input type="number" class="form-control form-control-sm dz-input"
@@ -496,6 +515,22 @@
           if (!hex || hex.length !== 12) return hex || '';
           return hex.match(/.{2}/g).join(':');
         },
+        formatAccel(c) {
+          if (!c?.accel_stream) return '—';
+          if (!c?.accel_valid) return '…';
+          return `${c.accel_x} / ${c.accel_y} / ${c.accel_z}`;
+        },
+        accelTitle(c) {
+          if (!c?.accel_stream) return 'Accel-Stream nicht aktiviert';
+          if (!c?.accel_valid) return 'Warte auf erste ESP-NOW Samples…';
+          const age = c.accel_age_ms != null ? `${c.accel_age_ms} ms alt` : '';
+          return `x=${c.accel_x} y=${c.accel_y} z=${c.accel_z} (raw LSB, ±2g)${age ? ' · ' + age : ''}`;
+        },
+        accelCellClass(c) {
+          if (!c?.accel_valid) return 'accel-stale';
+          if (c.accel_age_ms != null && c.accel_age_ms > 200) return 'accel-stale';
+          return '';
+        },
         formatSize(n) {
           if (n == null) return '';
           if (n < 1024) return n + ' B';
@@ -732,6 +767,44 @@
         async setMasterDeadzone() {
           await this.setDeadzone(0, this.masterDz);
         },
+        patchClientAccelStream(clientId, enabled) {
+          const clients = (this.state.clients || []).map((c) => {
+            if (c.id !== clientId) {
+              return c;
+            }
+            const next = { ...c, accel_stream: enabled };
+            if (!enabled) {
+              next.accel_valid = false;
+              next.accel_x = 0;
+              next.accel_y = 0;
+              next.accel_z = 0;
+              next.accel_age_ms = 0;
+            }
+            return next;
+          });
+          this.state = { ...this.state, clients };
+        },
+        async setAccelStream(clientId, enable) {
+          this.busy = true;
+          try {
+            const r = await fetch(`/api/clients/${clientId}/accel-stream`, {
+              method: 'PUT',
+              headers: { 'Content-Type': 'application/json' },
+              body: JSON.stringify({ enable: enable })
+            });
+            const data = await r.json();
+            if (!r.ok || !data.success) {
+              this.flash(data.error || `Accel-Stream Slave ${clientId} fehlgeschlagen`, false);
+              return;
+            }
+            this.patchClientAccelStream(clientId, !!data.enabled);
+            this.flash(`Slave ${clientId}: Accel-Stream ${data.enabled ? 'an' : 'aus'}`, true);
+          } catch (e) {
+            this.flash(String(e), false);
+          } finally {
+            this.busy = false;
+          }
+        },
         async setDeadzoneAll(deadzone) {
           if (deadzone == null || deadzone < 0) {
             this.flash('Ungültiger Deadzone-Wert', false);