[Bug]: CommonJS build throws ERR_REQUIRE_ESM on Node 20.0–20.18 and 22.0–22.11

Finding: In a reported case, requiring @a2a-js/sdk 1.2.1 from a CommonJS project fails with ERR_REQUIRE_ESM on Node 20.0–20.18 and 22.0–22.11. It reportedly works on Node 20.19+ and 22.12+ (https://github.com/a2aproject/a2a-js/issues/759). Reported symptom: running a one-line require of the package on Node 20.0.0 throws ERR_REQUIRE_ESM. The stack points at dist/index.cjs, which requires jose. The reporter's matrix lists failures on 20.0.0, 20.18.3 and 22.11.0, and successes on 20.19.0 and 22.22.2 (https://github.com/a2aproject/a2a-js/issues/759). Reported cause (not maintainer-confirmed): The reporter says jose v6 is ESM-only and the CJS bundles call require on it. They say Node permits require() of ESM only from 20.19 and 22.12, and that jose's README states the same range (https://github.com/a2aproject/a2a-js/issues/759). This is the reporter's analysis. No maintainer has confirmed it in the captured content. Why it may be missed: the reporter says CI runs only the latest 20.x, 22.x and 24.x, so older patch releases inside the declared node >=20 range are not exercised (https://github.com/a2aproject/a2a-js/issues/759). Diagnosis, if supported: if you see this error with this package, check the Node version first. The reporter's table associates the failure with Node below 20.19 on the 20 line and below 22.12 on the 22 line. Mitigation and fix status: the report implies upgrading Node to a version where require() of ESM works. The reporter also proposes raising the package engines field to ^20.19.0 || >=22.12.0. That is a suggestion only. The supplied sources show no fix commit, no merged change and no released fix, so fix status is UNKNOWN. Limitations: this is a single external report with a reporter-supplied version matrix. KFA did not reproduce it. The issue was open with no captured comments. The sources are about 12 days old relative to the as-of time, so the status may have changed since capture.