feat(IMP-11): D-2 — frame min_height_px hint (backend → UI)

Step 9 v4_all_judgments[] now exposes per-candidate min_height_px from
catalog frame_contracts.visual_hints.min_height_px (None when contract
unregistered). SlideCanvas pendingLayout zones render a red ring + 'min H
Npx' badge when zone height falls below the active frame's threshold.
Visual hint only; resize clamp (minSize=0.05) unchanged.

5 axes (single commit per Stage 5 plan):
- u1 backend: src/phase_z2_pipeline.py — Step 9 builder adds min_height_px
  via single get_contract(c.template_id) lookup; reuses _contract for
  catalog_registered (no double-lookup).
- u2 type: Front/client/src/types/designAgent.ts — FrameCandidate gains
  optional minHeightPx?: number.
- u3 mapper: Front/client/src/services/designAgentApi.ts — maps snake-case
  min_height_px → camelCase minHeightPx on v4_all_judgments path;
  v4_candidates fallback remains undefined (graceful).
- u4 active-frame lookup: Front/client/src/components/SlideCanvas.tsx —
  activeFrameId = overrideFrameId ?? defaultFrameId; activeCandidate via
  region.frame_candidates.find.
- u5 hint render: Front/client/src/components/SlideCanvas.tsx —
  zoneHeightPx = height * SLIDE_H (logical px, no double-apply); compare
  against activeCandidate.minHeightPx in pendingLayout mode only; red
  border + badge when below.

Tests: 5/5 pass in tests/test_phase_z2_step9_v4_all_judgments_min_height.py
(source-string + catalog-shape guards + None propagation, registered and
unregistered template_ids).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Front/client/src/components/SlideCanvas.tsx

@@ -612,6 +612,28 @@ export default function SlideCanvas({
               : null;
             const previewUrl = previewCandidate?.thumbnailUrl ?? null;
 
+            // IMP-11 u4: active frame lookup — distinct axis from preview.
+            // preview is shown only when override differs from default; active is
+            // always defined as override-if-present-else-default. Used by u5 to
+            // compare the active frame's catalog min_height_px against zone height.
+            const activeFrameId = overrideFrameId ?? defaultFrameId;
+            const activeCandidate = activeFrameId
+              ? region?.frame_candidates?.find((c) => c.id === activeFrameId)
+              : undefined;
+
+            // IMP-11 u5: catalog min_height_px violation hint. height is already
+            // a fraction of SLIDE_H (1280x720 logical px coordinate space), so
+            // logical px = height * SLIDE_H. measuredSlideBody.h is intentionally
+            // not re-multiplied (double-apply would shrink the comparison value).
+            // Hint is pendingLayout-only; resize clamp (minSize=0.05) is unchanged.
+            const zoneHeightPx = isPendingLayout ? height * SLIDE_H : null;
+            const minHeightPx = activeCandidate?.minHeightPx ?? null;
+            const belowMinHeight =
+              isPendingLayout &&
+              minHeightPx != null &&
+              zoneHeightPx != null &&
+              zoneHeightPx < minHeightPx;
+
             return (
               <div
                 key={zone.id}
@@ -695,6 +717,18 @@ export default function SlideCanvas({
                   </>
                 )}
 
+                {/* IMP-11 u5: red border + 'min H Npx' badge when zone height
+                    is below the active frame's catalog min_height_px. Visual
+                    hint only, no clamp/resize behavior change. */}
+                {belowMinHeight && minHeightPx != null && (
+                  <>
+                    <div className="absolute inset-0 pointer-events-none border-2 border-red-500" />
+                    <span className="absolute bottom-1 right-1 text-[9px] font-black uppercase tracking-tighter px-1.5 py-0.5 rounded bg-red-500 text-white shadow pointer-events-none">
+                      min H {minHeightPx}px
+                    </span>
+                  </>
+                )}
+
                 {/* zone 라벨 — 좌상단. 주 라벨 = section ids (S1, S1+S2),
                     부 라벨 = backend zone position (top, bottom, primary). */}
                 <div className="absolute top-1 left-1 flex items-center gap-1 pointer-events-none">

Front/client/src/services/designAgentApi.ts

@@ -527,6 +527,10 @@ export async function loadRun(runId: string): Promise<LoadRunResult> {
         // backend step09 의 catalog_registered (frame_contracts.yaml 등록 여부).
         // v4_all_judgments 에만 있음. v4_candidates fallback 시 undefined.
         catalogRegistered: c.catalog_registered,
+        // backend step09 의 min_height_px (frame_contracts.yaml visual_hints.min_height_px).
+        // logical 1280x720 px 좌표계. contract 미등록 또는 visual_hints 부재 시 undefined.
+        // v4_all_judgments 에만 있음. v4_candidates fallback 시 undefined (graceful).
+        minHeightPx: c.min_height_px ?? undefined,
       }));
 
     const displayStrategy = (

Front/client/src/types/designAgent.ts

@@ -127,6 +127,10 @@ export interface FrameCandidate {
   /** backend frame_contracts.yaml 에 catalog 등록 여부. false 면 사용자가 override
    *  시도해도 Step 7-A 가 skip (render path 미연결). UI 회색 + "render path 미적용" 표시. */
   catalogRegistered?: boolean;
+  /** IMP-11 D-2 — frame contract visual_hints.min_height_px (logical 1280x720 px).
+   *  Source = templates/phase_z2/catalog/frame_contracts.yaml visual_hints.min_height_px.
+   *  Undefined when contract unregistered or visual_hints absent (frontend tolerates undefined). */
+  minHeightPx?: number;
 }
 
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