fix(canvas): 创作工作台 - 参考内容槽位遵循模型上限并保留现有视觉

保留当前项目样式，仅吸收参考内容主槽位展示、模型上限收敛和对应行为测试。

Refs #232

web/test/creation-references.test.ts

@@ -0,0 +1,39 @@
+import { describe, expect, test } from "bun:test";
+
+import { canvasResourceMentionToken } from "../src/lib/canvas/canvas-resource-references";
+import type { CreationAttachment } from "../src/pages/create/creation-assets";
+import { buildCreationMentionReferences, reconcileCreationAttachmentLimit, removeCreationReferenceTokens } from "../src/pages/create/creation-references";
+
+function imageAttachment(id: string): CreationAttachment {
+    return {
+        id,
+        name: `${id}.png`,
+        type: "image/png",
+        dataUrl: `data:image/png;base64,${id}`,
+        previewUrl: `data:image/png;base64,${id}`,
+    };
+}
+
+describe("creation references", () => {
+    test("removes attachments and prompt tokens beyond the current model limit", () => {
+        const attachments = [imageAttachment("first"), imageAttachment("second"), imageAttachment("third")];
+        const references = buildCreationMentionReferences([], attachments);
+        const result = reconcileCreationAttachmentLimit(attachments, references, 1);
+        const prompt = references.map(canvasResourceMentionToken).join(" ");
+        const nextPrompt = removeCreationReferenceTokens(prompt, result.removedReferences);
+
+        expect(result.attachments).toEqual([attachments[0]]);
+        expect(result.removedReferences.map((reference) => reference.attachmentId)).toEqual(["second", "third"]);
+        expect(nextPrompt).toContain(canvasResourceMentionToken(references[0]));
+        expect(nextPrompt).not.toContain(canvasResourceMentionToken(references[1]));
+        expect(nextPrompt).not.toContain(canvasResourceMentionToken(references[2]));
+    });
+
+    test("returns the original attachment list when it is already within the limit", () => {
+        const attachments = [imageAttachment("first")];
+        const result = reconcileCreationAttachmentLimit(attachments, buildCreationMentionReferences([], attachments), 1);
+
+        expect(result.attachments).toBe(attachments);
+        expect(result.removedReferences).toEqual([]);
+    });
+});