fix(reporting): resolve report subjects through the canonical unified view and paginate the metric card grid

Two regressions surfaced by generating a real-mode agent report after a
backend restart:

- Report subject lookups used Monitor.GetUnifiedResources (the raw
  resource store), but the raw store's canonical IDs depend on per-boot
  ingest order for merged-source hosts: after a restart the same host
  resolved to a different agent-<hash> than the one the UI and
  /api/state advertise, so reports lost the resource name, availability,
  and metrics translation entirely. Subject enrichment now reads
  Monitor.UnifiedResourceSnapshot and MetricsTargetForResource resolves
  through GetUnifiedReadStateOrSnapshot first (raw store as fallback) -
  the same re-ingested registry every other read surface uses.
- The performance summary card grid positions cards absolutely and never
  paginated: an agent host reporting 8+ metric families walked off the
  page bottom, fought fpdf's auto page break, and scattered one orphan
  element per page (a 7-day delly report rendered 18 pages, ten of them
  near-blank). The grid now starts a new page before a row that will not
  fit; the same report renders 9 pages with intact cards.

Verified live: real-mode delly report shows name, 288 data points,
availability, charts, and correctly paginated cards. The underlying
canonical-ID instability (raw store vs re-ingested view, and the
resource_changes journal fragmenting across boot eras) is a separate
root issue tracked for its own fix.

pkg/reporting/pdf.go

@@ -884,6 +884,9 @@ func (g *PDFGenerator) writeSummarySection(pdf *fpdf.Fpdf, data *ReportData) {
 	startX := 20.0
 	rowStartY := pdf.GetY()
 
+	_, pageHeight := pdf.GetPageSize()
+	cardBottomLimit := pageHeight - 30
+
 	for i, metricType := range metricNames {
 		stats := data.Summary.ByMetric[metricType]
 		unit := GetMetricUnit(metricType)
@@ -898,6 +901,16 @@ func (g *PDFGenerator) writeSummarySection(pdf *fpdf.Fpdf, data *ReportData) {
 			pdf.SetY(rowStartY)
 		}
 
+		// The grid positions cards absolutely, so it must paginate
+		// itself: a row that would cross the bottom margin previously
+		// fought fpdf's auto page break and scattered one orphan
+		// element per page for the rest of the section.
+		if col == 0 && rowStartY+cardHeight > cardBottomLimit {
+			pdf.AddPage()
+			rowStartY = pdf.GetY()
+			pdf.SetY(rowStartY)
+		}
+
 		cardX := startX + float64(col)*(cardWidth+cardGap)
 		cardY := rowStartY
 
@@ -946,10 +959,9 @@ func (g *PDFGenerator) writeSummarySection(pdf *fpdf.Fpdf, data *ReportData) {
 		writeStat(cardX+46, statsY+6, "Samples", fmt.Sprintf("%d", stats.Count))
 	}
 
-	// Calculate final Y position based on number of rows
-	numRows := (len(metricNames) + 1) / 2 // Round up
-	finalY := rowStartY + float64(numRows)*(cardHeight+cardGap)
-	pdf.SetY(finalY)
+	// rowStartY tracks the current (possibly paginated) row, so the
+	// section ends just below the last row of cards.
+	pdf.SetY(rowStartY + cardHeight + cardGap)
 }
 
 // writeChartsSection writes charts for each metric.

pkg/reporting/pdf_ux_test.go

@@ -467,3 +467,46 @@ func TestGenerateMulti_FlowsResourceBlocksOntoSharedPages(t *testing.T) {
 		}
 	}
 }
+
+// TestSummarySection_PaginatesCardGridForManyMetrics pins the card grid's
+// self-pagination. Agent hosts report 8+ metric families; the absolutely
+// positioned grid previously walked off the page bottom and fought fpdf's
+// auto page break, scattering one orphan element per page for the rest of
+// the section (observed live as ten near-blank pages).
+func TestSummarySection_PaginatesCardGridForManyMetrics(t *testing.T) {
+	byMetric := map[string]MetricStats{}
+	for _, m := range []string{"cpu", "memory", "disk", "diskread", "diskwrite", "netin", "netout", "temperature", "iops", "usage"} {
+		byMetric[m] = MetricStats{Min: 1, Max: 9, Avg: 5, Current: 5, Count: 100}
+	}
+	data := &ReportData{
+		Title:        "Many metrics",
+		ResourceType: "agent",
+		ResourceID:   "agent-1",
+		Resource:     &ResourceInfo{Name: "host-01", Status: "online"},
+		Start:        time.Now().Add(-7 * 24 * time.Hour),
+		End:          time.Now(),
+		GeneratedAt:  time.Now(),
+		Summary:      MetricSummary{ByMetric: byMetric},
+		TotalPoints:  1000,
+	}
+
+	gen := NewPDFGenerator()
+	out, err := gen.Generate(data)
+	if err != nil {
+		t.Fatalf("Generate: %v", err)
+	}
+	text := extractPDFText(t, out)
+
+	pageTotal := regexp.MustCompile(`Page \d+ of (\d+)`).FindStringSubmatch(text)
+	if pageTotal == nil {
+		t.Fatalf("no page footer found in:\n%s", text)
+	}
+	if pages, _ := strconv.Atoi(pageTotal[1]); pages > 6 {
+		t.Fatalf("10-metric report rendered %d pages; the card grid must paginate compactly", pages)
+	}
+	for _, label := range []string{"Disk Read", "Network Out", "Temperature"} {
+		if !strings.Contains(text, label) {
+			t.Fatalf("metric card %q missing after pagination:\n%s", label, text)
+		}
+	}
+}