fix(video_compose): derive the Remotion theme from real playbook keys

`_build_theme_from_playbook` documents itself as reading "a playbook's actual
color values [...] not picked from a preset menu", but three of the keys it
reads are not in the playbook schema, so each silently fell back to a
hardcoded default for every playbook:

    typo.get("heading")        schema key is `headings`
    palette.get("muted_text")  schema key is `muted`
    motion.get("pace")         `pace` is an identity field; motion carries
                               pacing_rules, not a pace enum

Effect, before -> after:

    flat-motion-graphics  headingFont  Inter -> Space Grotesk
                          muted        #6B7280 -> #64748B
                          spring       20/120 @0.4s -> 12/80 @0.3s  (pace: fast)
    minimalist-diagram    headingFont  Inter -> IBM Plex Sans
    anime-ghibli          headingFont  Inter -> Noto Serif JP

Every playbook rendered its headings in Inter regardless of what it declared,
and no playbook's declared pace ever reached the spring config.

This is the Remotion counterpart of the HyperFrames style-bridge defect in
issue #306. That bridge lives in lib/hyperframes_style_bridge.py and is
untouched here, as are the open PRs against it (#296, #307).

Two adjacent things deliberately left alone:

- `palette.get("surface", bg)` also names a key the schema does not define,
  but the fallback to the background color is an explicit, sensible default
  rather than a dropped value. Giving playbooks a real surface color would be
  a schema addition, not a bug fix.
- The pace branch still handles only `fast` and `slow`, so `deliberate` and
  `rapid` land on the moderate default. Extending that mapping is a motion
  tuning decision, not part of reading the right key.

Note on ordering: Root.tsx's resolveTheme currently prefers a named preset
over themeConfig, which meant this derived theme was discarded whenever the
playbook name matched a Remotion preset — masking the defect. Fixing
resolveTheme before this would have made every video lose its heading
typeface, muted color and motion pacing at once.

Expectations in the new tests come from the playbook YAML rather than a
hardcoded table, so a playbook that changes its typeface keeps them honest.

Verified: 4 cases fail on the unfixed tree; full suite goes 964 -> 977 passed
with no regressions.

Author: bbudaedu

tests/contracts/test_remotion_theme_playbook_keys.py

@@ -0,0 +1,88 @@
+"""The Remotion theme must be derived from the playbook's real schema keys.
+
+`VideoCompose._build_theme_from_playbook` says it reads "a playbook's actual
+color values [...] not picked from a preset menu", but it read three keys the
+playbook schema does not define, so each silently fell back to a hardcoded
+default for every playbook:
+
+    typo.get("heading")        schema key is `headings`
+    palette.get("muted_text")  schema key is `muted`
+    motion.get("pace")         `pace` is an identity field, not a motion one
+
+Expectations come from the playbook YAML rather than a hardcoded table, so a
+playbook that changes its typeface keeps this honest.
+
+This is the Remotion counterpart of the HyperFrames style-bridge defect in
+issue #306; that bridge lives in lib/hyperframes_style_bridge.py and is not
+touched here.
+"""
+
+from pathlib import Path
+
+import pytest
+import yaml
+
+from styles.playbook_loader import list_playbooks
+from tools.video.video_compose import VideoCompose
+
+REPO_ROOT = Path(__file__).resolve().parents[2]
+STYLES_DIR = REPO_ROOT / "styles"
+
+PLAYBOOK_NAMES = sorted(list_playbooks())
+
+
+def _raw(name: str) -> dict:
+    return yaml.safe_load((STYLES_DIR / f"{name}.yaml").read_text(encoding="utf-8"))
+
+
+def _theme(name: str) -> dict:
+    theme = VideoCompose()._build_theme_from_playbook(name, {})
+    if not theme:
+        pytest.skip(f"{name} does not currently yield a theme")
+    return theme
+
+
+@pytest.mark.parametrize("name", PLAYBOOK_NAMES)
+def test_heading_font_comes_from_the_playbook(name: str) -> None:
+    """Regression: read from `heading`, so every playbook rendered in Inter."""
+    expected = _raw(name)["typography"]["headings"]["font"]
+    assert _theme(name)["headingFont"] == expected
+
+
+@pytest.mark.parametrize("name", PLAYBOOK_NAMES)
+def test_muted_text_color_comes_from_the_playbook(name: str) -> None:
+    """Regression: read from `muted_text`, so this was always #6B7280."""
+    palette = _raw(name)["visual_language"]["color_palette"]
+    if "muted" not in palette:
+        pytest.skip(f"{name} declares no muted color")
+    assert _theme(name)["mutedTextColor"] == palette["muted"]
+
+
+def test_identity_pace_drives_the_motion_feel() -> None:
+    """Regression: read `pace` off motion, where the schema has no such key,
+    so the spring never left its moderate default."""
+    fast = [n for n in PLAYBOOK_NAMES if _raw(n)["identity"]["pace"] == "fast"]
+    if not fast:
+        pytest.skip("no playbook declares a fast pace")
+
+    moderate_default = {"damping": 20, "stiffness": 120, "mass": 1}
+    for name in fast:
+        theme = _theme(name)
+        assert theme["springConfig"] != moderate_default, (
+            f"{name} declares pace=fast but still got the moderate spring"
+        )
+        assert theme["transitionDuration"] < 0.4
+
+
+@pytest.mark.parametrize("name", PLAYBOOK_NAMES)
+def test_derived_theme_only_reads_documented_palette_keys(name: str) -> None:
+    """The derived colors must be values the playbook can actually express."""
+    palette = _raw(name)["visual_language"]["color_palette"]
+    theme = _theme(name)
+
+    primary = palette["primary"]
+    accent = palette["accent"]
+    assert theme["primaryColor"] == (primary[0] if isinstance(primary, list) else primary)
+    assert theme["accentColor"] == (accent[0] if isinstance(accent, list) else accent)
+    assert theme["backgroundColor"] == palette["background"]
+    assert theme["textColor"] == palette["text"]

tools/video/video_compose.py

@@ -1253,7 +1253,7 @@ def _build_theme_from_playbook(
             bg = palette.get("background", "#FFFFFF")
             text = palette.get("text", "#1F2937")
             surface = palette.get("surface", bg)
-            muted = palette.get("muted_text", "#6B7280")
+            muted = palette.get("muted", "#6B7280")
 
             # Build chart colors from all palette entries
             chart_colors = []
@@ -1271,7 +1271,7 @@ def _build_theme_from_playbook(
                 "surfaceColor": surface,
                 "textColor": text,
                 "mutedTextColor": muted,
-                "headingFont": typo.get("heading", {}).get("font", "Inter"),
+                "headingFont": typo.get("headings", {}).get("font", "Inter"),
                 "bodyFont": typo.get("body", {}).get("font", "Inter"),
                 "monoFont": typo.get("code", {}).get("font", "JetBrains Mono"),
                 "chartColors": chart_colors[:6],
@@ -1287,9 +1287,9 @@ def _build_theme_from_playbook(
                 else f"rgba(15, 23, 42, 0.75)"
             )
 
-            # Motion style from playbook
-            motion = playbook.get("motion", {})
-            pace = motion.get("pace", "moderate")
+            # Motion style from playbook. `pace` is an identity field in the
+            # playbook schema; motion carries pacing_rules, not a pace enum.
+            pace = playbook.get("identity", {}).get("pace", "moderate")
             if pace == "fast":
                 theme["springConfig"] = {"damping": 12, "stiffness": 80, "mass": 1}
                 theme["transitionDuration"] = 0.3