fix(canvas/test): use string keys in TIER_CONFIG toHaveProperty calls

Vitest's toHaveProperty is string-keyed; TypeScript strict mode with
noPropertyAccessFromIndexSignature rejects numeric literal keys on
Record<number, TIER_CONFIG_LEVEL>.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

canvas/src/lib/__tests__/statusDotClass.test.ts

@@ -55,10 +55,10 @@ describe("statusDotClass", () => {
 
 describe("TIER_CONFIG", () => {
   it("has entries for all four tier levels", () => {
-    expect(TIER_CONFIG).toHaveProperty(1);
-    expect(TIER_CONFIG).toHaveProperty(2);
-    expect(TIER_CONFIG).toHaveProperty(3);
-    expect(TIER_CONFIG).toHaveProperty(4);
+    expect(TIER_CONFIG).toHaveProperty("1");
+    expect(TIER_CONFIG).toHaveProperty("2");
+    expect(TIER_CONFIG).toHaveProperty("3");
+    expect(TIER_CONFIG).toHaveProperty("4");
   });
 
   it("each tier has label, color, and border fields", () => {