feat(report): draw the USBM RI8507 compliance chart on the event report

Replace the "[compliance chart coming soon]" placeholder in
_draw_mic_and_usbm with a real inset axes calling
sfm.compliance.draw_compliance_chart on rd.channels / rd.sample_rate_sps
(the full-rate in/s waveform samples). Title updated "USBM RI8507 And OSMRE"
→ "USBM RI8507" — we draw only the RI8507 lines (Drywall 0.75 + plaster 0.50);
the OSMRE overlay is dropped by choice.

Waveform events only (the histogram layout has no USBM chart). Falls back to a
"(no waveform data)" note when samples are unavailable. Closes the 1.0
compliance-chart blocker.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01YDXjZCr4RqT2U3QvMDhgzf

sfm/report_pdf.py

@@ -578,15 +578,16 @@ def _draw_mic_and_usbm(ax, rd: ReportData) -> None:
         _kv(ax, 0.0, y, label, value, label_w=0.18)
         y -= 0.15
 
-    # USBM chart placeholder — upper-right.  Real piecewise compliance
-    # curves are a separate work item; for now this just shows the title
-    # + a "see report" message so the layout is correct.
-    ax.text(0.72, 0.97, "USBM RI8507 And OSMRE",
-            fontsize=9, weight="bold", color="#333", ha="center", va="top",
-            transform=ax.transAxes)
-    ax.text(0.72, 0.50, "[compliance chart\ncoming soon]",
-            fontsize=8, color="#bbb", ha="center", va="center",
-            transform=ax.transAxes, style="italic")
+    # USBM RI8507 compliance chart — inset axes in the right half of this band.
+    ax.text(0.74, 1.00, "USBM RI8507", fontsize=9, weight="bold", color="#333",
+            ha="center", va="top", transform=ax.transAxes)
+    if rd.channels and rd.sample_rate_sps:
+        from sfm.compliance import draw_compliance_chart
+        inset = ax.inset_axes([0.52, 0.02, 0.46, 0.82])
+        draw_compliance_chart(inset, rd.channels, rd.sample_rate_sps)
+    else:
+        ax.text(0.74, 0.48, "(no waveform data)", fontsize=8, color="#bbb",
+                ha="center", va="center", transform=ax.transAxes, style="italic")
 
 
 def _mic_rows(rd: ReportData) -> list[tuple[str, Optional[str]]]: