fix: avoid context-window-too-small misclassification (#1266, thanks @humanwritten)

Co-authored-by: humanwritten <humanwritten@users.noreply.github.com>

src/agents/pi-embedded-helpers.islikelycontextoverflowerror.test.ts

@@ -0,0 +1,34 @@
+import { describe, expect, it } from "vitest";
+import { isLikelyContextOverflowError } from "./pi-embedded-helpers.js";
+import { DEFAULT_AGENTS_FILENAME } from "./workspace.js";
+
+const _makeFile = (overrides: Partial<WorkspaceBootstrapFile>): WorkspaceBootstrapFile => ({
+  name: DEFAULT_AGENTS_FILENAME,
+  path: "/tmp/AGENTS.md",
+  content: "",
+  missing: false,
+  ...overrides,
+});
+
+describe("isLikelyContextOverflowError", () => {
+  it("matches context overflow hints", () => {
+    const samples = [
+      "Model context window is 128k tokens, you requested 256k tokens",
+      "Context window exceeded: requested 12000 tokens",
+      "Prompt too large for this model",
+    ];
+    for (const sample of samples) {
+      expect(isLikelyContextOverflowError(sample)).toBe(true);
+    }
+  });
+
+  it("excludes context window too small errors", () => {
+    const samples = [
+      "Model context window too small (minimum is 128k tokens)",
+      "Context window too small: minimum is 1000 tokens",
+    ];
+    for (const sample of samples) {
+      expect(isLikelyContextOverflowError(sample)).toBe(false);
+    }
+  });
+});