fix: use valid CSS color space names in toValue()

colorjs uses internal short names (p3, a98rgb, prophoto) that don't
match the CSS predefined color space identifiers required by the spec:
  - p3      → display-p3
  - a98rgb  → a98-rgb
  - prophoto → prophoto-rgb

This caused toValue() to emit invalid CSS like `color(p3 ...)`, which
the css-tree lexer rejects when re-validating the value in the CSS value
input (e.g. after a round-trip through the style panel).

Author: kof

packages/css-engine/src/core/to-value.test.ts

@@ -331,7 +331,7 @@ describe("Convert WS CSS Values to native CSS strings", () => {
       components: [0.8, 0.4, 0.6],
       alpha: 0.8,
     });
-    expect(value).toBe("color(p3 0.8 0.4 0.6 / 0.8)");
+    expect(value).toBe("color(display-p3 0.8 0.4 0.6 / 0.8)");
   });
 
   test("color with xyz-d65 uses color() function", () => {
@@ -361,7 +361,7 @@ describe("Convert WS CSS Values to native CSS strings", () => {
       components: [0.4, 0.6, 0.3],
       alpha: { type: "var", value: "tw-bg-opacity" },
     });
-    expect(value).toBe("color(p3 0.4 0.6 0.3 / var(--tw-bg-opacity))");
+    expect(value).toBe("color(display-p3 0.4 0.6 0.3 / var(--tw-bg-opacity))");
   });
 
   test("color in tuple", () => {

packages/css-engine/src/core/to-value.ts

@@ -112,11 +112,15 @@ export const toValue = (
         return `oklab(${c1} ${c2} ${c3} / ${alpha})`;
       case "oklch":
         return `oklch(${c1} ${c2} ${c3} / ${alpha})`;
-      // Fall back to color() function for less common color spaces
+      // Fall back to color() function for less common color spaces.
+      // Webstudio uses colorjs internal names; map to CSS predefined color space names.
       case "p3":
-      case "srgb-linear":
+        return `color(display-p3 ${c1} ${c2} ${c3} / ${alpha})`;
       case "a98rgb":
+        return `color(a98-rgb ${c1} ${c2} ${c3} / ${alpha})`;
       case "prophoto":
+        return `color(prophoto-rgb ${c1} ${c2} ${c3} / ${alpha})`;
+      case "srgb-linear":
       case "rec2020":
       case "xyz-d65":
       case "xyz-d50":