feat(IMP-14): A-4 — slide_base embedded vs standalone mode contract

Step 13 owns iframe-vs-standalone CSS contract in slide_base.html via
3-valued embedded_mode enum (auto / embedded / standalone). Removes
SlideCanvas.tsx runtime CSS injection workaround; frontend now passes
?embedded=1 query so auto-mode script attaches html.embedded class and
scopes the standalone body centering/min-height/padding reset.

- templates/phase_z2/slide_base.html: conditional html.embedded class +
  CSP-safe auto-mode <script> + additive html.embedded body/.slide rules
- src/phase_z2_pipeline.py: render_slide gains keyword-only embedded_mode
  ("auto" default) + ValueError guard; 3 existing call sites unchanged
- Front/client/src/components/SlideCanvas.tsx: derive embeddedSrc with
  ?embedded=1 (query-preserving), drop reset CSS injection block
- tests/phase_z2/test_slide_base_embedded_mode.py: 6 cases — auto script,
  CSS rules, embedded/standalone explicit modes, byte-determinism,
  invalid-mode guard

Front/client/src/components/SlideCanvas.tsx

@@ -186,6 +186,12 @@ export default function SlideCanvas({
   // 슬라이드 박스 표시 조건 — final.html 있거나 pendingLayout 모드.
   const showSlideBox = (finalHtmlUrl || isPendingLayout) && !isPipelineRunning;
 
+  // IMP-14 (Step 13 A-4) — backend slide_base.html 가 embedded vs standalone CSS
+  // contract 를 `?embedded=1` query 로 소유. 기존 query string 보존하면서 flag 만 추가.
+  const embeddedSrc = finalHtmlUrl
+    ? `${finalHtmlUrl}${finalHtmlUrl.includes("?") ? "&" : "?"}embedded=1`
+    : undefined;
+
   // wrapper 는 scaled 크기를 가지므로 layout 상 fit. 안의 슬라이드는 1280×720 으로
   // top-left origin scale 후 wrapper 안에 정확히 맞춤.
   const W_SCALED = SLIDE_W * scale;
@@ -283,37 +289,21 @@ export default function SlideCanvas({
           >
             <iframe
               ref={iframeRef}
-              src={finalHtmlUrl}
+              src={embeddedSrc}
               title="Phase Z 렌더 결과"
               className="w-full h-full border-0 block"
               scrolling="no"
               sandbox="allow-same-origin"
               style={{ pointerEvents: isEditMode ? "auto" : "none" }}
               onLoad={(e) => {
-                // final.html 은 standalone 표시용으로 body 에 padding / flex center /
+                // IMP-14 (Step 13 A-4) — embedded vs standalone CSS reset 은 backend
-                // min-height: 100vh 가 있어서, iframe 안에서는 슬라이드가 잘림.
+                // slide_base.html 가 `?embedded=1` query 로 소유. frontend 가 더 이상
-                // .slide (1280×720) 만 보이도록 reset CSS 를 contentDocument 에 주입.
+                // reset CSS 를 contentDocument 에 inject 하지 않음. embedded query 가
+                // backend auto-mode detection script 를 trigger 해서 html.embedded
+                // class 를 붙이고 standalone-only body 규칙을 reset.
                 try {
                   const doc = (e.currentTarget as HTMLIFrameElement).contentDocument;
                   if (!doc) return;
-                  const style = doc.createElement("style");
-                  style.textContent = `
-                    html, body {
-                      margin: 0 !important;
-                      padding: 0 !important;
-                      min-height: 0 !important;
-                      height: 720px !important;
-                      width: 1280px !important;
-                      background: transparent !important;
-                      display: block !important;
-                      overflow: hidden !important;
-                    }
-                    .slide {
-                      box-shadow: none !important;
-                      margin: 0 !important;
-                    }
-                  `;
-                  doc.head.appendChild(style);
 
                   // 2026-05-14 — slide-level override CSS (catalog/template 무변).
                   // Home 이 mdx 별 default visual 보완 (bullet 간격 / zone 비율 등) 지정.

src/phase_z2_pipeline.py

@@ -2021,12 +2021,23 @@ def _attempt_salvage_chain(
 
 def render_slide(slide_title: str, slide_footer: Optional[str],
                  zones_data: list[dict], layout_preset: str,
-                 layout_css: dict, gap_px: int = GRID_GAP) -> str:
+                 layout_css: dict, gap_px: int = GRID_GAP,
+                 *, embedded_mode: str = "auto") -> str:
     """Single slide HTML — slide_base.html + 8-preset layout vocabulary.
 
     layout_css = build_layout_css() 결과 — areas/cols/rows 문자열 + 동적 heights flag.
     Template 은 layout_css.{areas,cols,rows} 를 grid CSS 에 직접 주입.
+
+    embedded_mode (IMP-14): "auto" | "embedded" | "standalone". Controls
+    slide_base.html body CSS contract. Default "auto" preserves backward-compat
+    with run_overflow_check standalone path and lets iframe consumers signal via
+    ?embedded=1 or window.self!==window.top.
     """
+    if embedded_mode not in ("auto", "embedded", "standalone"):
+        raise ValueError(
+            f"render_slide: invalid embedded_mode={embedded_mode!r}; "
+            "expected one of 'auto', 'embedded', 'standalone'"
+        )
     env = Environment(
         loader=FileSystemLoader(str(TEMPLATE_DIR)),
         autoescape=select_autoescape(["html"]),
@@ -2050,6 +2061,7 @@ def render_slide(slide_title: str, slide_footer: Optional[str],
         layout_css=layout_css,
         gap_px=gap_px,
         token_css=_read_token_css(),
+        embedded_mode=embedded_mode,
     )
 
 

templates/phase_z2/slide_base.html

@@ -1,11 +1,23 @@
 <!-- Phase Z-2 MVP-1.5b — single slide + Type B layout (top/bottom zones).
      원래 Phase Z 설계 복귀: MDX 1 = slide 1, layout preset = zone 분할, frame-derived block ⊂ zone. -->
 <!DOCTYPE html>
-<html lang="ko">
+<html lang="ko"{% if embedded_mode == "embedded" %} class="embedded"{% endif %}>
 <head>
   <meta charset="UTF-8">
   <meta name="viewport" content="width=1280">
   <title>{{ slide_title }}</title>
+  {% if embedded_mode == "auto" %}
+  <script>
+  (function(){
+    try {
+      var params = new URLSearchParams(window.location.search);
+      if (params.get('embedded') === '1' || window.self !== window.top) {
+        document.documentElement.classList.add('embedded');
+      }
+    } catch (e) {}
+  })();
+  </script>
+  {% endif %}
   <style>
     /* ── existing tokens (inlined) ── */
     {{ token_css | safe }}
@@ -20,6 +32,19 @@
       padding: 20px 0;
     }
 
+    /* ── IMP-14 A-4: embedded mode reset (iframe consumer) ──
+         standalone-only body centering/min-height/padding undone so the .slide
+         (1280×720) sits at origin without vertical shift or clipping. */
+    html.embedded body {
+      background: transparent;
+      display: block;
+      min-height: 0;
+      padding: 0;
+    }
+    html.embedded .slide {
+      box-shadow: none;
+    }
+
     /* ── 16:9 슬라이드 (single, 1280×720) ── */
     .slide {
       width: 1280px; height: 720px;

tests/phase_z2/test_slide_base_embedded_mode.py

@@ -0,0 +1,69 @@
+"""IMP-14 A-4 — slide_base.html embedded_mode contract tests.
+
+Asserts the three-valued enum (auto / embedded / standalone) round-trips
+through render_slide -> slide_base.html, that the additive html.embedded
+CSS reset and the auto-mode detection <script> are emitted under the
+correct modes, that the invalid-mode guard raises ValueError, and that
+Jinja2 rendering is byte-deterministic across calls.
+"""
+from __future__ import annotations
+
+import pytest
+
+from src.phase_z2_pipeline import render_slide
+
+
+def _zone() -> dict:
+    return {"position": "primary", "template_id": "__empty__", "slot_payload": {}}
+
+
+def _layout_css() -> dict:
+    return {"areas": '"primary"', "cols": "1fr", "rows": "1fr"}
+
+
+def _render(embedded_mode: str = "auto") -> str:
+    return render_slide(
+        slide_title="t",
+        slide_footer=None,
+        zones_data=[_zone()],
+        layout_preset="single",
+        layout_css=_layout_css(),
+        gap_px=14,
+        embedded_mode=embedded_mode,
+    )
+
+
+def test_auto_script_present():
+    html = _render("auto")
+    assert "params.get('embedded')" in html
+    assert "window.self !== window.top" in html
+    assert "classList.add('embedded')" in html
+
+
+def test_css_rules_present():
+    html = _render("auto")
+    assert "html.embedded body" in html
+    assert "html.embedded .slide" in html
+
+
+def test_embedded_mode_explicit():
+    html = _render("embedded")
+    assert '<html lang="ko" class="embedded">' in html
+    assert "params.get('embedded')" not in html
+
+
+def test_standalone_mode_explicit():
+    html = _render("standalone")
+    assert '<html lang="ko">' in html
+    assert 'class="embedded"' not in html.split("</head>")[0]
+    assert "params.get('embedded')" not in html
+
+
+def test_deterministic():
+    assert _render("embedded") == _render("embedded")
+    assert _render("auto") == _render("auto")
+
+
+def test_invalid_mode_raises():
+    with pytest.raises(ValueError, match="invalid embedded_mode"):
+        _render("bogus")