refactor: collapse mask definition registry to a single keyed registry

The freeform mask was assembled on every getMaskDefinition("freeform") call,
re-spreading params and injecting a wrong SquareIcon placeholder, with a type
cast to suppress the structural mismatch. Root cause: MasksRegistry was keyed
on BuiltinMaskType, so freeform had no entry.

- Re-key MasksRegistry from BuiltinMaskType to MaskType
- Register freeform alongside builtins in registerDefaultMasks, with
  PenToolAddIcon as its menu icon
- getMaskDefinition and getMaskDefinitionsForMenu become plain registry
  lookups with no branching, no manual spreading, no cast
- Rename RegisteredBuiltinMaskDefinition to RegisteredMaskDefinition and
  tighten computeParamUpdate return type to Partial<BaseMaskParams>

Co-authored-by: Cursor <cursoragent@cursor.com>

1 files changed, 7 insertions, 29 deletions

diff --git a/apps/web/src/masks/index.ts b/apps/web/src/masks/index.ts
index be5faef7..994f05f2 100644
--- a/apps/web/src/masks/index.ts
+++ b/apps/web/src/masks/index.ts
@@ -1,15 +1,9 @@
 import type { Mask, MaskDefaultContext, MaskType } from "@/masks/types";
-import {
-	BASE_MASK_PARAM_DEFINITIONS,
-	builtinMasksRegistry,
-	type RegisteredBuiltinMaskDefinition,
-} from "./registry";
-import { freeformMaskDefinition } from "./freeform/definition";
+import { masksRegistry } from "./registry";
 import { generateUUID } from "@/utils/id";
-import { SquareIcon } from "@hugeicons/core-free-icons";
 
-export { builtinMasksRegistry } from "./registry";
-export { registerBuiltinMasks as registerDefaultMasks } from "./builtin/definitions";
+export { masksRegistry } from "./registry";
+export { registerDefaultMasks } from "./builtin/definitions";
 
 type MaskWithoutId = Mask extends infer TMask
 	? TMask extends Mask
@@ -40,28 +34,12 @@ function withMaskId({ mask, id }: { mask: MaskWithoutId; id: string }): Mask {
 	}
 }
 
-export function getMaskDefinition(maskType: MaskType): RegisteredBuiltinMaskDefinition {
-	if (maskType === "freeform") {
-		return {
-			...freeformMaskDefinition,
-			params: [...freeformMaskDefinition.params, ...BASE_MASK_PARAM_DEFINITIONS],
-			icon: { icon: SquareIcon },
-		} as RegisteredBuiltinMaskDefinition;
-	}
-
-	return builtinMasksRegistry.get(maskType);
+export function getMaskDefinition(maskType: MaskType) {
+	return masksRegistry.get(maskType);
 }
 
 export function getMaskDefinitionsForMenu() {
-	return [
-		...builtinMasksRegistry.getAll(),
-		{
-			...freeformMaskDefinition,
-			name: "Pen tool",
-			params: [...freeformMaskDefinition.params, ...BASE_MASK_PARAM_DEFINITIONS],
-			icon: { icon: SquareIcon },
-		},
-	];
+	return masksRegistry.getAll();
 }
 
 export function buildDefaultMaskInstance({
@@ -71,7 +49,7 @@ export function buildDefaultMaskInstance({
 	maskType: MaskType;
 	elementSize?: { width: number; height: number };
 }): Mask {
-	const definition = getMaskDefinition(maskType);
+	const definition = masksRegistry.get(maskType);
 	const context: MaskDefaultContext = { elementSize };
 	return withMaskId({
 		mask: definition.buildDefault(context),