hub: HostCapabilityChecker — operator alert on agent capability-degraded (v0.19.0)

Companion to felhom-agent v0.44.0. New monitor.HostCapabilityChecker (sibling of
HostStalenessChecker) reads the capabilities snapshot from the latest host report and emits
agent_capability_degraded/recovered (operator-only, 1h cooldown) on ok<->degraded transitions
for any Critical capability. store.GetHostCapabilities (MAX(id), no migration). Goldens mirror
the new capabilities field.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01EPZ4GJ8L5Jqf8UiPwbn1kt

hub/internal/store/store.go

@@ -1624,3 +1624,52 @@ func (s *Store) GetHostStaleness() ([]HostStaleRow, error) {
 	}
 	return out, rows.Err()
 }
+
+// CapabilityStatus mirrors the agent's capability.Status wire shape (felhom-agent v0.44.0): one
+// privileged `sudo -n` grant the non-root agent depends on, and whether it is currently usable.
+type CapabilityStatus struct {
+	Name     string `json:"name"`
+	Feature  string `json:"feature"`
+	Critical bool   `json:"critical"`
+	Status   string `json:"status"` // "ok" | "degraded"
+	Reason   string `json:"reason,omitempty"`
+}
+
+// HostCapabilityRow is the per-host capability snapshot the HostCapabilityChecker reads — extracted
+// from the latest host-report's report_json (no dedicated column; the array rides the report body).
+type HostCapabilityRow struct {
+	HostID       string
+	CustomerID   string
+	Capabilities []CapabilityStatus
+}
+
+// GetHostCapabilities returns the latest capability snapshot per host (from the most recent
+// host_reports row). Hosts whose latest report carries no capabilities array (a pre-v0.44.0 agent)
+// yield an empty slice — the checker treats that as "ok/unknown" and never alerts, so an old agent
+// can't trip a false degraded.
+func (s *Store) GetHostCapabilities() ([]HostCapabilityRow, error) {
+	rows, err := s.db.Query(`
+		SELECT hr.host_id, hr.customer_id, hr.report_json
+		FROM host_reports hr
+		JOIN (SELECT host_id, MAX(id) AS mx FROM host_reports GROUP BY host_id) latest
+		  ON hr.id = latest.mx`)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+	var out []HostCapabilityRow
+	for rows.Next() {
+		var r HostCapabilityRow
+		var reportJSON string
+		if err := rows.Scan(&r.HostID, &r.CustomerID, &reportJSON); err != nil {
+			return nil, err
+		}
+		var body struct {
+			Capabilities []CapabilityStatus `json:"capabilities"`
+		}
+		_ = json.Unmarshal([]byte(reportJSON), &body) // a malformed/old body → nil caps → no alert
+		r.Capabilities = body.Capabilities
+		out = append(out, r)
+	}
+	return out, rows.Err()
+}