Endless v0.4

Endless v0.4 — Engine trust fixes

This release fixes correctness bugs found in review and caps the supported
build range to what Minecraft 1.20.1 can safely represent.

Behavior changes:

• Build height is capped to vanilla's guarded packed BlockPos envelope:
  min >= -2032, max <= 2032 (exclusive top, highest placeable Y = 2031).
  Previously advertised ±2,097,152 was not representable — packed positions
  and block-update packets silently wrapped beyond the 12-bit Y envelope. The
  16-block guard band at each edge matches vanilla's DimensionType span and
  keeps neighboring-position operations from wrapping to the opposite end.
• Minecraft 1.20.1 chunk files store each section's absolute section Y as a
  signed byte (-128..127, raw block coverage [-2048, 2048)). v0.4 never
  reinterprets wrapped section coordinates during migration.
• The build range is persisted per world in data/endless_build_heights.dat.
  It is read before any level is created, so chunk deserialization uses the
  world's layout. Once persisted, effective range = union(world, config):
  widening expands the world; a narrower config cannot shrink the persisted
  world range and make saved sections unreachable.
• Played pre-v0.4 worlds now pass a fail-closed migration gate before any
  ServerLevel/chunk is loaded. Because pre-v0.4 used one global endless.json,
  the current raw config is only a migration candidate, not proof of a
  particular world's historical layout. The exact pre-clamp config is
  preserved until classification completes, then all dimension region files
  are inspected before the candidate is accepted.
• Saved normal section payloads or block entities outside the candidate range
  prove that a played world had a wider historical section array and stop
  migration, even when the saved section's block palette is air-only. Saved
  heightmap packing is also checked against the raw legacy span; for example a
  64-long 1.20.1 heightmap paired with a current narrow config is conflicting
  history and fails closed instead of being rebuilt under a guessed range.
• Raw edge ranges such as [-2048, 2048) may clamp away section Y=-128/Y=127
  only when those guard sections are provably air-only and contain no block
  entity. Non-air blocks, malformed edge data, unreadable region data, ranges
  outside the signed-byte section-Y envelope, spans over 4096 blocks, or an
  untrusted legacy config stop startup instead of risking silent section loss.
  World range metadata is created only after migration succeeds.
• Existing but unreadable/invalid v0.4 world-range metadata also fails closed
  rather than being treated as missing and replaced from the current config.
• Multiplayer servers are authoritative during the login phase, before
  ClientboundLoginPacket constructs the client world and before any chunk data
  can arrive. Fabric uses a login query held open until the client applies the
  range; Forge uses a login packet plus protocol/version gating.
• Every new remote login now forces the vanilla baseline from the
  ClientHandshakePacketListenerImpl constructor, not from ClientboundHelloPacket.
  This covers offline-mode servers that skip the authentication hello entirely
  and prevents an applied range from a failed previous login leaking into the
  next connection. Integrated-server memory connections preserve the shared
  server-authoritative range.
• Chunk sections are real LevelChunkSection instances across the configured
  range, matching vanilla invariants for saving, networking, lighting and mod
  integrations.
• Height values are normalized to 16-block section boundaries.
• Malformed configs use defaults in memory and are copied to
  endless.json.broken when possible. Config normalization is deferred until
  world migration has been classified; if the malformed-file backup cannot be
  created, the original config is never overwritten automatically.

Fixes:

• Removed custom ChunkAccess section masks/helpers; vanilla highest-filled,
  isYSpaceEmpty and findBlocks logic runs unchanged.
• Restored vanilla lighting-storage lifecycle and copy-on-write semantics by
  removing synthetic DataLayer overrides.
• Left vanilla below-zero retrogen accessors untouched.
• Removed the duplicate Heightmap mixin; vanilla sizes heightmaps from the
  effective chunk height and rebuilds incompatible persisted layouts only
  after v0.4 has first verified that the saved packing agrees with migration
  history.
• Removed global SimpleBitStorage error suppression.
• Removed the old synchronous chunk-loading section cleanup and sparse/null
  section machinery.
• The client render grid is now a 32-section camera-following vertical window
  with hysteresis instead of a fixed slab anchored at minBuildHeight.
• Waystones compatibility reads the effective world/server-authoritative max
  instead of the live file config.
• Fabric and Forge both synchronize build height before client world creation;
  failed/rejected logins cannot leave stale authoritative range state for the
  next connection, including an offline-mode vanilla-server follow-up.
• Release workflow checks changelog/tag collisions before builds/uploads,
  validates exact loader artifacts, gates publishing behind tests/live joins,
  and does not publish merely because a PR merged to master.
• Development run tasks are loader-explicit (runFabricClient,
  runForgeClient, runFabricServer, runForgeServer); ambiguous bare runClient /
  runServer selectors fail with a clear message.

Developer / validation:

• PR Validate workflow compiles/tests the shared, Fabric and Forge projects.
• Unit regressions cover the guarded envelope, config overflow/preservation,
  world-range merging, fail-closed legacy classification, changed-global-config
  history (including saved Y=37 sections), 64-long heightmap disagreement,
  raw-edge section handling, and storage.
• Real-client live-join CI covers: extended server authority, an Endless server
  with vanilla range against an extended client config, and a genuine Mojang
  offline-mode vanilla server against an extended Endless client config, on
  both loaders. The vanilla-server scenario deliberately pre-seeds applied=true
  with an extended stale range before connection, so the every-connection
  constructor reset is exercised instead of relying on a fresh JVM baseline.

Known limitations:

• True heights beyond the guarded packed-Y envelope require replacing position
  serialization and are out of scope.
• Vanilla clients cannot join an extended-range Endless server.
• Free-camera mods can move the camera independently of the player; the render
  window may wait for the next vanilla-triggered update before following it.
• Maximum-height memory/GC behavior is a separate performance validation item.
  Empty vanilla sections use compact single-value palettes and lazy light data,
  but 254 real section object graphs per chunk are still ~10.6x vanilla's 24;
  fresh-world profiling at vanilla, 128-section and 254-section ranges remains
  required before treating maximum-height OOM behavior as resolved.

What's Changed

• fix: cap range to packed Y envelope and restore vanilla section invariants (v0.4) by @UpperMoon0 in #1

New Contributors

• @UpperMoon0 made their first contribution in #1

Full Changelog: v0.3...v0.4