fix: use local timezone in console log timestamps

formatConsoleTimestamp previously used Date.toISOString() which always
returns UTC time (suffixed with Z). This confused users whose local
timezone differs from UTC.

Now uses local time methods (getHours, getMinutes, etc.) and appends the
local UTC offset (e.g. +08:00) instead of Z. The pretty style returns
local HH:MM:SS. The hasTimestampPrefix regex is updated to accept both
Z and +/-HH:MM offset suffixes.

Closes #14699

src/logging/console-timestamp.test.ts

@@ -0,0 +1,39 @@
+import { describe, expect, it } from "vitest";
+import { formatConsoleTimestamp } from "./console.js";
+
+describe("formatConsoleTimestamp", () => {
+  it("pretty style returns local HH:MM:SS", () => {
+    const result = formatConsoleTimestamp("pretty");
+    expect(result).toMatch(/^\d{2}:\d{2}:\d{2}$/);
+    // Verify it uses local time, not UTC
+    const now = new Date();
+    const expectedHour = String(now.getHours()).padStart(2, "0");
+    expect(result.slice(0, 2)).toBe(expectedHour);
+  });
+
+  it("compact style returns local ISO-like timestamp with timezone offset", () => {
+    const result = formatConsoleTimestamp("compact");
+    // Should match: YYYY-MM-DDTHH:MM:SS.mmm+HH:MM or -HH:MM
+    expect(result).toMatch(/^\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}\.\d{3}[+-]\d{2}:\d{2}$/);
+    // Should NOT end with Z (UTC indicator)
+    expect(result).not.toMatch(/Z$/);
+  });
+
+  it("json style returns local ISO-like timestamp with timezone offset", () => {
+    const result = formatConsoleTimestamp("json");
+    expect(result).toMatch(/^\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}\.\d{3}[+-]\d{2}:\d{2}$/);
+    expect(result).not.toMatch(/Z$/);
+  });
+
+  it("timestamp contains the correct local date components", () => {
+    const before = new Date();
+    const result = formatConsoleTimestamp("compact");
+    const after = new Date();
+    // The date portion should match the local date
+    const datePart = result.slice(0, 10);
+    const beforeDate = `${before.getFullYear()}-${String(before.getMonth() + 1).padStart(2, "0")}-${String(before.getDate()).padStart(2, "0")}`;
+    const afterDate = `${after.getFullYear()}-${String(after.getMonth() + 1).padStart(2, "0")}-${String(after.getDate()).padStart(2, "0")}`;
+    // Allow for date boundary crossing during test
+    expect([beforeDate, afterDate]).toContain(datePart);
+  });
+});