test(P5): re-render deck + add layout/aspect-ratio/theme-structural tests (REQ-262)

Re-rendered HTML + PPTX via render_slides.sh (pinned marp-cli@4.5.0,
mermaid-cli@11.16.0, 2x transparent PNGs). 22 slides (title + 20 main
+ 1 appendix), 23 media files embedded. Theme embedded in HTML
(--sp-red + padding confirmed).

Added 9 tests to test_slides_pipeline.py (the gap that let the layout
regression through):
- test_theme_css_has_section_padding (REQ-254)
- test_theme_css_suppresses_title_chrome (REQ-256)
- test_theme_css_has_aspect_ratio_aware_images (REQ-255)
- test_png_aspect_ratios_sane (REQ-259/260, scoped to deck-referenced
  PNGs only per GRILL revision 1, bounds [0.4, 4.0])
- test_render_slides_has_2x_scale (REQ-258)
- test_render_slides_pins_cli_versions (REQ-257)
- test_render_deck_removed (REQ-257)
- test_html_embeds_theme (REQ-262)
- test_html_slide_count_matches_marp (REQ-262)

32 slide tests pass (23 original + 9 new). 94 tests pass across key
files. run_platform.sh --check-only exit 0.

---ci---
project: acdl
phase: 5
milestone: v1.22
status: execute
phase_role: execution
---/ci---

tests/test_slides_pipeline.py

@@ -267,4 +267,107 @@ def test_source_md_no_badges():
     """REQ-252: no maturity badges in the source-of-truth markdown."""
     text = SOURCE_MD.read_text()
     assert "badge" not in text.lower(), \
-        "Source markdown still contains badge spans"
+        "Source markdown still contains badge spans"
+
+
+# --- v1.22 layout/aspect-ratio/theme-structural tests (REQ-262) ---
+
+def test_theme_css_has_section_padding():
+    """REQ-254: theme CSS has a section padding rule (root cause fix)."""
+    css = THEME_CSS.read_text()
+    assert "padding:" in css, "theme CSS has no padding rule"
+    # The section rule must have padding (not just table/td padding)
+    assert re.search(r"section\s*\{[^}]*padding:", css, re.DOTALL), \
+        "theme CSS has no padding on the section rule"
+
+
+def test_theme_css_suppresses_title_chrome():
+    """REQ-256: title slides suppress header/footer chrome."""
+    css = THEME_CSS.read_text()
+    assert "section.title header" in css, \
+        "theme CSS does not suppress title-slide header"
+    assert "section.title footer" in css, \
+        "theme CSS does not suppress title-slide footer"
+    assert "display: none" in css, \
+        "theme CSS does not set display:none on title chrome"
+
+
+def test_theme_css_has_aspect_ratio_aware_images():
+    """REQ-255: image rules use object-fit + max-width (not blunt max-height only)."""
+    css = THEME_CSS.read_text()
+    assert "object-fit" in css, \
+        "theme CSS does not use object-fit for images"
+    assert "max-width" in css, \
+        "theme CSS does not set max-width for images"
+
+
+def test_png_aspect_ratios_sane():
+    """REQ-259/260: PNGs referenced in the marp deck have aspect ratios
+    in [0.4, 4.0] (suitable for 16:9 slides with img.tall/img.wide classes).
+    Only checks PNGs actually referenced in the current marp deck —
+    legacy/unused PNGs are not checked (GRILL revision 1)."""
+    import struct
+    deck_text = MARP_DECK.read_text()
+    # Extract all referenced PNG paths: ![...](assets/png/X.png)
+    referenced = re.findall(r'!\[[^\]]*\]\(assets/png/([^)]+\.png)\)', deck_text)
+    assert referenced, "no PNGs referenced in the marp deck"
+    for png_name in referenced:
+        png_path = ASSETS / "png" / png_name
+        assert png_path.is_file(), f"referenced PNG not found: {png_name}"
+        with open(png_path, "rb") as fh:
+            data = fh.read(24)
+        assert data[:8] == b"\x89PNG\r\n\x1a\n", f"{png_name} is not a PNG"
+        w = struct.unpack(">I", data[16:20])[0]
+        h = struct.unpack(">I", data[20:24])[0]
+        ar = w / h
+        assert 0.4 <= ar <= 4.0, \
+            f"{png_name} aspect ratio {ar:.2f} outside [0.4, 4.0] ({w}x{h})"
+
+
+def test_render_slides_has_2x_scale():
+    """REQ-258: render_slides.sh uses -s 2 (2x scale) and -b transparent."""
+    text = RENDER_SCRIPT.read_text()
+    assert "-s 2" in text, "render_slides.sh does not use -s 2 (2x scale)"
+    assert "-b transparent" in text, \
+        "render_slides.sh does not use -b transparent"
+
+
+def test_render_slides_pins_cli_versions():
+    """REQ-257: render_slides.sh pins marp-cli and mermaid-cli versions
+    (no @latest)."""
+    text = RENDER_SCRIPT.read_text()
+    assert "marp-cli@" in text, "render_slides.sh does not pin marp-cli"
+    assert "mermaid-cli@" in text, \
+        "render_slides.sh does not pin mermaid-cli"
+    assert "@latest" not in text, \
+        "render_slides.sh still uses @latest (not pinned)"
+
+
+def test_render_deck_removed():
+    """REQ-257: render_deck.sh has been deleted (produced unthemed output)."""
+    old_script = ROOT / "scripts" / "render_deck.sh"
+    assert not old_script.exists(), \
+        "render_deck.sh still exists (should be deleted — produced unthemed output)"
+
+
+def test_html_embeds_theme():
+    """REQ-262: the committed HTML embeds the S&P theme (--sp-red + padding
+    in the inline <style> block)."""
+    html = (PRESENTATIONS / "nova-autonomous-cloud-delivery.html").read_text()
+    assert "--sp-red" in html, "committed HTML does not embed --sp-red"
+    assert "padding:" in html, "committed HTML does not embed padding rule"
+
+
+def test_html_slide_count_matches_marp():
+    """REQ-262: the committed HTML <section> count matches the marp deck
+    slide count (title + 20 main + 1 appendix = 22)."""
+    html = (PRESENTATIONS / "nova-autonomous-cloud-delivery.html").read_text()
+    section_count = html.count("<section ")
+    deck_text = MARP_DECK.read_text()
+    main_slides = len(re.findall(r"^## Slide ", deck_text, re.MULTILINE))
+    appendix_slides = len(re.findall(r"^## Appendix ", deck_text, re.MULTILINE))
+    # +1 for the title slide (which is an H1, not "## Slide")
+    expected = main_slides + appendix_slides + 1
+    assert section_count == expected, \
+        f"HTML has {section_count} sections, expected {expected} " \
+        f"({main_slides} main + {appendix_slides} appendix + 1 title)"