feat: publish standalone worker

Separate worker packaging and service lifecycle from the control plane.

internal/webapp/templates/logs.html

@@ -0,0 +1,17 @@
+{{define "body"}}<section class="card">
+  <h1>Worker logs</h1>
+  <p class="muted">In-memory ring buffer (capacity {{.BufferCap}}, holding {{.BufferSize}} lines). Phase 1 shows worker-binary logs only; stack and host logs land in later phases.</p>
+  <form method="get" action="/logs" class="tail-form">
+    <label>Show last
+      <select name="tail" onchange="this.form.submit()">
+        <option value="200" {{if eq .Tail 200}}selected{{end}}>200</option>
+        <option value="500" {{if eq .Tail 500}}selected{{end}}>500</option>
+        <option value="1000" {{if eq .Tail 1000}}selected{{end}}>1000</option>
+        <option value="5000" {{if eq .Tail 5000}}selected{{end}}>5000</option>
+      </select>
+    </label>
+    <noscript><button type="submit">Apply</button></noscript>
+  </form>
+  <pre class="log">{{range .Lines}}{{.}}
+{{end}}</pre>
+</section>{{end}}