fix(#75): IMP-47A mdx03 frontend execution stabilization (u1~u4)

u1: SlideCanvas iframe sandbox += allow-scripts (allow-same-origin preserved)
    → embedded-mode script in slide_base.html now applies html.embedded
    → standalone CSS reset deactivates inside iframe; no clipping
u2: designAgentApi.loadRun merges candidate_evidence + v4_all_judgments
    + v4_candidates via Map<template_id|id|frame_id> dedup,
    LABEL_PRIORITY (use_as_is<light_edit<restructure<reject) then
    confidence desc, capped TOP_N_FRAMES=6
u3: Home.handleGenerate useCallback deps = [uploadedFile, slidePlan,
    userSelection, pendingZones, pendingLayout] (5-tuple, stale-closure fix)
u4: tests/manual/imp47a_e2e.md — mdx03 manual e2e spec (5 axes)

Frontend-only. Backend src/ untouched. No template/catalog edits.
Determinism preserved (no LLM in frontend merge logic).
Baseline: pytest -q tests → 623 passed.

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

Front/client/src/components/SlideCanvas.tsx

@@ -293,7 +293,7 @@ export default function SlideCanvas({
               title="Phase Z 렌더 결과"
               className="w-full h-full border-0 block"
               scrolling="no"
-              sandbox="allow-same-origin"
+              sandbox="allow-same-origin allow-scripts"
               style={{ pointerEvents: isEditMode ? "auto" : "none" }}
               onLoad={(e) => {
                 // IMP-14 (Step 13 A-4) — embedded vs standalone CSS reset 은 backend