feat(ai): added 2020-12 schema migration to ai strict validation

- Added draft-07-to-2020-12 schema upgrade logic for `$schema`, `definitions`, `$ref`, tuple, and nullable mapping.
- Integrated `upgradeJsonSchemaTo202012` into strict adaptation, validation, strict-mode, sanitizer, and wire/dereference flows.
- Replaced set-based traversal helpers with record maps, `for...in` loops, and epoch/`once` cycle guards.
- Added unreleased changelog entries and tests for schema normalization, `oneOf` to `anyOf`, and tuple validation edge cases.

packages/ai/test/schema-normalization.test.ts

@@ -6,8 +6,10 @@ import {
 	sanitizeSchemaForCCA,
 	sanitizeSchemaForGoogle,
 	sanitizeSchemaForStrictMode,
+	schemaNeedsDraft202012Upgrade,
 	stripResidualCombiners,
 	tryEnforceStrictSchema,
+	upgradeJsonSchemaTo202012,
 } from "@oh-my-pi/pi-ai/utils/schema";
 
 // ---------------------------------------------------------------------------
@@ -94,6 +96,64 @@ describe("sanitizeSchemaForStrictMode", () => {
 	});
 });
 
+// ---------------------------------------------------------------------------
+// upgradeJsonSchemaTo202012
+// ---------------------------------------------------------------------------
+
+describe("upgradeJsonSchemaTo202012", () => {
+	it("infers draft-07 tuple and dependency keywords without a $schema URI", () => {
+		const schema = {
+			type: "object",
+			properties: {
+				definitions: { type: "string" },
+				tuple: {
+					type: "array",
+					items: [{ type: "string" }, { type: "integer" }],
+					additionalItems: false,
+				},
+				gated: {
+					type: "object",
+					dependencies: {
+						a: ["b"],
+						c: { required: ["d"] },
+					},
+				},
+			},
+			definitions: {
+				Ref: { type: "string" },
+			},
+		};
+
+		expect(schemaNeedsDraft202012Upgrade(schema)).toBe(true);
+		expect(upgradeJsonSchemaTo202012(schema)).toEqual({
+			type: "object",
+			properties: {
+				definitions: { type: "string" },
+				tuple: {
+					type: "array",
+					prefixItems: [{ type: "string" }, { type: "integer" }],
+					items: false,
+				},
+				gated: {
+					type: "object",
+					dependentRequired: { a: ["b"] },
+					dependentSchemas: { c: { required: ["d"] } },
+				},
+			},
+			$defs: {
+				Ref: { type: "string" },
+			},
+		});
+	});
+
+	it("returns unchanged schemas by identity when no draft upgrade is needed", () => {
+		const schema = { type: "object", properties: { name: { type: "string" } } };
+
+		expect(schemaNeedsDraft202012Upgrade(schema)).toBe(false);
+		expect(upgradeJsonSchemaTo202012(schema)).toBe(schema);
+	});
+});
+
 // ---------------------------------------------------------------------------
 // sanitizeSchemaForGoogle
 // ---------------------------------------------------------------------------