time: an invalid --local-timezone crashes the server with a traceback

[cliffhall]

Problem

An invalid --local-timezone value makes serve() raise before the stdio transport opens, so the process dies with a Python traceback.

Where it is pinned

src/time/tests/test_protocol.py: test_invalid_local_timezone_fails_before_the_transport_opens, added in #4972 (Wave 1 of #4857). Each of these tests carries a KNOWN BUG marker: it asserts the current, wrong behavior, so the fix has to change it.

Expected

A one-line error naming the invalid timezone, with a non-zero exit.

Done when

• The behavior above is fixed, in the legacy-era (2025-11-25) server on SDK 1.x.
• The pinning tests assert the correct behavior, and their KNOWN BUG markers are gone.
• The per-file 90% coverage gate still passes.

[cliffhall]

Fixed by #5027, merged into v2/main.