Add configurable token limit and truncation warning to Lab 1 confidence chat

src/lib/lab1-confidence.test.ts

@@ -2,10 +2,12 @@ import { describe, expect, it } from "vitest";
 
 import {
   extractLab1AssistantContent,
+  extractLab1FinishReason,
   extractLab1ResponseTokens,
   formatProbabilityPercent,
   getConfidenceBand,
   logprobToProbabilityPercent,
+  parseLab1MaxTokens,
 } from "~/lib/lab1-confidence";
 
 describe("logprobToProbabilityPercent", () => {
@@ -30,6 +32,28 @@ describe("extractLab1AssistantContent", () => {
   });
 });
 
+describe("extractLab1FinishReason", () => {
+  it("reads the upstream finish reason when it is present", () => {
+    expect(
+      extractLab1FinishReason({
+        choices: [
+          {
+            finish_reason: "length",
+          },
+        ],
+      }),
+    ).toBe("length");
+  });
+});
+
+describe("parseLab1MaxTokens", () => {
+  it("uses a bounded positive environment override", () => {
+    expect(parseLab1MaxTokens("768")).toBe(768);
+    expect(parseLab1MaxTokens("999999")).toBe(2048);
+    expect(parseLab1MaxTokens("nope")).toBe(512);
+  });
+});
+
 describe("extractLab1ResponseTokens", () => {
   it("maps token logprobs and alternate candidates into display data", () => {
     expect(