OnlyWorlds Unity SDK 0.2.0

Install via Package Manager -> Add package from git URL:

https://github.com/OnlyWorlds/unity-sdk.git?path=/Packages/com.onlyworlds.sdk

Reading worlds from disk, writing them back safely, and a guard on the vendored schema. Verified
against a 142-test EditMode suite and, for the first time, a real stripped IL2CPP build.

Added

• OWFolderReader / OWFolderLoader — read an OnlyWorlds world folder from disk (spec v0.3.5)
  and load it into a cache keyed (Folder, worldId, folderPath). Reading is not editing: no
  directories, dot-folders or marker files are created, and no file is ever rewritten — including to
  normalise a key spelling. Files that cannot be used are reported, never deleted; one malformed
  file never costs you the rest of the world. Verified against a second implementation's
  conformance fixture.
• OWBrowserWindow → Open Folder… — the reader, reachable.
• OWEdit — typed edits that PATCH only what changed. Diffs a baseline snapshot, so it needs
  nothing from the model and works for generated types that do not exist yet. Sends nothing when
  nothing changed, because a no-op PATCH still bumps updated_at and shows up as a phantom edit in
  everyone else's change feed.
• OWClient.BulkAsync with OWBulkResult — bulk writes whose partial failures are hard to
  ignore. A bulk request returns HTTP 200 even when individual slots failed, so the per-slot
  status is the only place the truth lives.
• OWSchemaPin + drift guard — the vendored presentation sidecar is hash-checked against the
  pinned distribution on every test run. The pin is (tag, manifest hash), never the tag alone: a
  tag is mutable, and moving one regenerates a self-consistent manifest that cannot detect its own
  tag having moved.

Fixed

• Extension fields survived JSON but not Unity's own serializer. OWElement did not implement
  ISerializationCallbackReceiver, so the methods carrying the bag across a Unity serialization
  pass were never called. An element held in a MonoBehaviour or ScriptableObject field lost
  every x_* field.
• Every field was serialized twice — name and Name. Newtonsoft defaults to OptOut, so
  public properties went to the wire beside their attributed fields. The server ignores the
  PascalCase copies, which is why it survived a day of green tests.
• Incremental sync could advance its cursor past changes it never applied, if the changes feed
  reported more pages but gave no cursor to reach them — silently losing them forever.
• The rewind diagnostic reported the wrong cursor, rendering "Cursor 100 was ahead of server
  head 100". The value it existed to report was overwritten before the message was built.
• OWMainThread.Run queued work into silence when no pump existed: the task never completed and
  never faulted, hanging the caller with an empty console. It throws now, and says what to do.
• OWWorldCache.Upsert left an element in its old type bucket when its type changed — reachable
  by the folder reader on the first file whose body contradicts its directory.
• HasChangesAsync's two-directional truth is documented rather than surprising.

Validated

• The nullable converter survives IL2CPP stripping. Against a real stripped Android build: five
  closed SerializableNullable<T> instantiations, three closed converter instantiations, the
  factory reflectable in global-metadata.dat, and ReadJson/WriteJson as executable methods.
  Runtime behaviour on device is still unproven — the probe's verdict only prints on hardware.