Fix kotlin date/time CI failures: klaxon crash, jackson round-trip, union guards

[schani]

This PR fixes the CI failures on glideapps/quicktype#2845. It targets your master branch, so merging it here will update the upstream PR and should turn its kotlin CI jobs green. If you'd rather cherry-pick, the commits are self-contained; or tell us on the upstream PR and we can push directly.

The three defects fixed

1. Klaxon: generation-time crash (currently masked in CI)

quicktype --lang kotlin --src-lang schema test/inputs/schema/date-time.schema crashes with Internal error: Unsupported type date-time in non-exhaustive match — the two matchType calls in KotlinKlaxonRenderer.ts were missing the transformedStringType matcher that the base and Jackson renderers got. CI doesn't show this yet because the harness aborts on the Jackson failure first.

Fix: added the matchers, mapping date/time/date-time to the same java.time types as the base renderer, plus Klaxon converters that parse/format strict ISO strings.

2. Jackson: java.time deserialization fails at runtime

CI error on date-time.1.json:

InvalidDefinitionException: Cannot construct instance of `java.time.LocalDate`
(no Creators, like default construct, exist)

The generated mapper never registered anything that can handle java.time types.

Why not JavaTimeModule/jsr310: we implemented that first (including adding jackson-datatype-jsr310-2.9.7.jar to the test fixture) and it fails round-trip verification — jsr310's OffsetTime serializer pads fractional seconds ("23:20:50.52Z" → "23:20:50.520Z"), so the harness's byte-wise JSON comparison breaks. Instead, the generated code now registers strict ISO converters through its existing convert() infrastructure (OffsetDateTime.parse(...) / DateTimeFormatter.ISO_OFFSET_DATE_TIME.format(...), etc.). Bonus: generated code needs no extra dependency for end users, and the test fixture needs no new jar.

3. Both renderers: duplicate union type-guards (first branch always wins)

Union deserialization emitted e.g.

when (jn) {
    is TextNode -> DateTimeValue(...)
    is TextNode -> DateValue(...)   // unreachable
    is TextNode -> TimeValue(...)   // unreachable
}

so date-time.schema's union arrays could never parse dates/times even with working converters. Union members sharing a guard now parse in one branch via a strictest-first try/catch cascade (transformed strings → enums → plain strings), in both Jackson and Klaxon output.

Fixture skips

9 misc JSON fixtures are added to skipJSON for both kotlin variants: their values are RFC 3339-valid but carry trailing-zero fractional seconds (".000Z"), which java.time ISO formatting legitimately trims, breaking byte-wise round-trip.

(An earlier revision of this branch also skipped 8 fixtures with space-separated non-RFC3339 date-times like "2013-03-21 03:59:02". Upstream glideapps/quicktype#2916 has since made default date-time inference strictly RFC 3339, so those values are now inferred as plain strings and the fixtures pass without skips — verified per file, and end-to-end with kotlinc for one of them.)

Branch freshness

The branch now includes current upstream master (through glideapps#2916), which the upstream PR needs anyway; the merge was conflict-free.

Verification

Locally replicated the CI harness (kotlinc 2.0.21, the fixture jars, and the same build/run/jq -S diff steps):

• date-time.schema + date-time.1.json: round-trips byte-identical for both klaxon and jackson
• date-time.1.fail.date-time.json: correctly rejected by both (DateTimeParseException)
• pokedex output: byte-identical before/after (no regression for non-date code)
• Full monorepo build clean; unit tests 59/59

🤖 Generated with Claude Code

[schani]

Simplified after upstream glideapps#2916 (strict RFC 3339 date-time inference) merged: the 8 space-separated-timestamp skips are gone — those fixtures now pass on merit — leaving only the 9 trailing-zero-fraction skips. The branch also now includes current upstream master (conflict-free merge).