calibrate a confidence threshold from one inference pass

Threshold calibration ran the model over every tile once per threshold — three
GPU passes to compare 0.50, 0.25 and 0.15 on a hundred-tile raster. The answer
is already in a single run at the lowest value: detections above a higher cut
are a subset of it, and duplicate suppression walks candidates in descending
confidence, so a lower-confidence box can never displace a higher-confidence
one. The kept set above any cut is identical whichever threshold the run used,
which is what makes one pass sufficient rather than merely cheaper.

QA now takes calibration_thresholds and reads each operating point off the same
precision/recall walk it already performs, marking the F1-optimal cut. The lab
runs inference once and fills its table from the sweep.

The contract test asserted the per-threshold loop by name, pinning the waste it
was meant to describe. It now states what calibration owes an operator: a row
per requested threshold, from one run.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

frontend/src/types.ts

@@ -1431,6 +1431,25 @@ export interface DetectionQaRequest {
   iou_threshold: number
   class_name?: string | null
   min_confidence?: number | null
+  /**
+   * Confidence cuts to report next to the run's own operating point. They are
+   * read off one matching pass, so a sweep costs no extra inference.
+   */
+  calibration_thresholds?: number[]
+}
+
+/** One confidence cut, derived from a single run rather than a run of its own. */
+export interface DetectionCalibrationPoint {
+  min_confidence: number
+  confidence_threshold: number | null
+  candidate_count: number
+  true_positives: number
+  false_positives: number
+  false_negatives: number
+  precision: number | null
+  recall: number | null
+  f1_score: number | null
+  best_f1_in_sweep: boolean
 }
 
 export interface DetectionQaResult {
@@ -1486,6 +1505,7 @@ export interface DetectionQaResult {
     envelope_precision_recall_curve?: PrecisionRecallCurve
   }
   precision_recall_curve?: PrecisionRecallCurve
+  calibration_sweep?: DetectionCalibrationPoint[]
 }
 
 /**