fix-bugs-dont-reproduce, scoped per the keeper rule: jolt-if19 (a leading + on a
numeric literal errored instead of reading as the positive number) is fixed in
jolt.reader (read-number* now strips a leading + like -, positive), the code we
keep. The Janet seed reader (reader.janet) is left untouched — it's deleted in
Phase 5, so fixing it is wasted work.
Since the seed reader stays buggy, reader-parity can't use it as the oracle for
these inputs: added check-correct to assert the portable reader against the hand-
verified value (+5 => 5, +42, +0xff => 255, +3.5). reader-parity 67/67. No Janet
binary/gate impact (jolt.reader is not yet in the binary path). jolt-if19.
afada6d4ff