## Summary
Two small additive changes a derived spawner needs.
- **`BaseSpawner.OnTick()` is now `virtual`.** A subclass that gates spawning on external state (time windows, event triggers) must gate *timer* spawns without gating the manual `Spawn()` API, and `OnTick` is the only place the two paths differ: it is the timer callback and `Spawn()` is both what it calls and what commands and scripts call. Cost: one virtual dispatch on the existing timer callback; no change to stock behaviour.
- **`group` in the JSON DTO.** `BaseSpawner.Group` (all dead, then respawn) is binary-persisted but was missing from `SpawnerDto`, so it did not survive export/import. Added to the abstract record after `spawnLocationIsHome`, assigned in `ApplyDto` after `InitSpawn` (which resets it), and exported by the three stock `ToDto` implementations.
## Test plan
- [x] A derived spawner overriding `OnTick` with a closed gate: `OnTick()` spawns nothing; manual `Spawn()` still spawns and does not pass through `OnTick`.
- [x] DTO round trip with `Group = true` carries `group` and restores it on `ToSpawner()`.
- [x] `UOContent.Tests` full suite green.
- [ ] CI
## Summary
Moves spawner entry storage out of the abstract `BaseSpawner` into the concrete owner, so a spawner subclass can store its own entry type while every stock code path keeps working. Motivation: an out-of-tree spawner (ModernSpawner) needs `ModernSpawnerEntry : SpawnerEntry` with extra fields; today `BaseSpawner` owns `List<SpawnerEntry>` and a family of non-virtual members, and the serialization generator constructs list elements from the declared element type, so storage has to live in the class that declares the concrete list.
### What changed
- **`BaseSpawner` v13** no longer owns `_entries`. It reads entries through an abstract view and mutates them through an owner contract (`BaseSpawner.Entries.cs`):
`Entries` (`IReadOnlyList<SpawnerEntry>`, `[IgnoreDupe]`), `EntrySpan` (`ReadOnlySpan<SpawnerEntry>` for hot loops), `CreateEntry`, `AddEntryCore`, `RemoveEntryCore`, `ClearEntriesCore`, `AdoptEntries`, `CloneEntry`, `TransferSpawned`, plus public `RemoveAllEntries()`, `CopyEntriesTo(target)` and protected `RebuildSpawned()`. Every loop inside `BaseSpawner` is an indexed `for` over `EntrySpan`.
- **`Spawner` v2** owns `[SerializedIgnoreDupe] List<SpawnerEntry> _entryList` (generated `EntryList`, protected). `ProximitySpawner`/`RegionSpawner` inherit it unchanged. The `Spawned` rebuild and timer re-arm moved from the base `[AfterDeserialization]` (which runs before derived fields are read) into `Spawner`'s.
- **Save migration**: `MigrateFrom(V12Content)` (and the v10/v11/legacy readers) hand the old list to the owner via `AdoptEntries`; `Spawner.MigrateFrom(V1Content)` restores its own fields and leaves the adopted list alone. Three v12/v1/v0 save blobs captured before the change are committed as fixtures and loaded by tests.
- **Lifecycle hooks** (`BaseSpawner.Hooks.cs`, all no-op by default): `OnStarted`, `OnStopped`, `OnBeforeSpawn(entry)` veto, `OnConfigureSpawned(entry, spawned)` before positioning, entry-aware `GetSpawnPosition(entry, spawned, map)`, `OnSpawned(entry, spawned)`, `OnSpawnedDeath(entry, spawned, killer)`. `BaseCreature.OnDeath` calls `NotifySpawnedDeath` before base death (which deletes the mobile and unlinks the spawner). `Start()` and the `NextSpawn` setter share one start core so `OnStarted` fires on both.
- **`SpawnerEntry` v2**: per-entry `Disabled` (XmlSpawner's entry "lock"), stored inverted so the common case writes nothing in binary or JSON; skipped by weighted selection, live spawns untouched; toggle button per row in `SpawnerGump`. `SetParent` is public and `Parent` is protected so an out-of-tree entry subclass can adopt and dirty-track.
- **DTO**: `SpawnerDto` loses `Entries`; each concrete record declares its own `entries` at the same JSON order, so `Distribution/Data/Spawns/**` is byte-identical. Import adopts the deserialized entry objects instead of recreating them through `AddEntry`, which is what preserves subtype fields (and `disabled`).
### Breaking changes and behaviour changes
- **API:** `BaseSpawner.Entries` is `IReadOnlyList<SpawnerEntry>` instead of `List<SpawnerEntry>`. The generated `AddToEntries`/`RemoveFromEntries`/`InsertIntoEntries`/`RemoveFromEntriesAt`/`ClearEntries` helpers on `BaseSpawner` are gone; use `AddEntry`/`RemoveEntry`/`RemoveAllEntries`/`CopyEntriesTo`. `RemoveAllEntries()` deletes the entries' live spawns as well as the entries (the old generated `ClearEntries()` only cleared the list), which is why it has a new name rather than the old one.
- `SpawnerControllerGump` "copy entries" now goes through `CopyEntriesTo`, which deletes the target's live spawns (previously it cleared the list and left the spawns orphaned) and is a no-op when source == target (previously that wiped the source).
- `RemoveEntry` with an entry the spawner does not own is now a no-op (previously it deleted that entry's spawns).
- `Respawn()` honours `Disabled` because it calls `Spawn()`; `Spawn(int index)`, `RemoveSpawn`, and `RemoveSpawns` ignore it.
- Copying entries between spawners no longer forces a 1-second first spawn; the target re-arms on its normal delay.
- Subclasses that own a different entry list than `Spawner`'s must call `RebuildSpawned()` from their own `[AfterDeserialization]` (`Spawner`'s call runs before their list is read) and, when converting adopted entries into their own type, carry live spawns across with `TransferSpawned`. The in-repo test subclass demonstrates both.
### Performance
Manual harness (`Benchmark_SpawnPath_Manual`, skipped by default): 100k calls, entries all full so `Spawn()` does selection only.
| Path | Before (4bad0cc9e) | After |
|---|---|---|
| `Spawn()` 1 entry | 48.7 ns | 53.2 ns (within run-to-run noise) |
| `Spawn()` 10 entries | 243.7 ns | 153.1 ns |
| `Spawn()` 50 entries | 1077.6 ns | 645.1 ns |
| `Remove()` 10 entries | 139.6 ns | 83.6 ns |
Hooks are no-ops for stock spawners; `OnMovement` is untouched.
### Tests
- `SpawnerEntryOwnershipTests` (add/remove/clear, start after stop, dupe, copy, self-copy, foreign-entry removal, Disabled binary/JSON)
- `SpawnerHookTests` (hook order for mobiles and items, veto, death notification, `NextSpawn` start, a subclass with its own `List<TestEntry>` round-tripping and duping)
- `SpawnerSaveMigrationTests` (v12 fixtures through `Spawner`, `ProximitySpawner`, `RegionSpawner`; new-format byte-identical round trip with a live spawn reference)
- `SpawnerDtoEntryTests` (compact JSON position of `entries`, `disabled` only when set, import adopts the deserialized objects)
- Existing DTO/JSON/spawn-data tests unchanged. UOContent.Tests 801 passed, Server.Tests 869 passed. Migration schemas regenerated (`BaseSpawner.v13`, `Spawner.v2`, `SpawnerEntry.v2`).
Coverage caveats, stated plainly: v10, v11 and the pre-codegen legacy reader could not be captured as fixtures by the current code; each changed only `_entries = …` → `AdoptEntries(…)` into the same sink the v12 fixtures exercise, and is covered by review. The captured v12 fixtures carry no live spawns, so re-linking live `ISpawnable` references is proven by the new-format round trip, not by a legacy blob. The `SpawnerGump` toggle layout could not be checked in a client; the delete button moved from x=38 to x=46 to make room.
## Summary
Removes the dated `DynamicJson` JSON helper and migrates spawner JSON (de)serialization to a polymorphic `record SpawnerDto` hierarchy. `DynamicJson` was the last remaining consumer (regions moved off it in #1400).
The key correctness improvement: **System.Text.Json deserializes plain DTO records, never a live `Item`.** Previously, deserializing directly into an `Item` meant STJ constructed world-registered objects *before* the data was validated — a malformed/hand-edited spawn file could leave orphaned spawner Items in the world save. Now a parse failure is GC-only; `dto.ToSpawner()` constructs the spawner only from a fully-validated DTO and self-cleans on failure.
## What changed
- **New:** `SpawnerDto` (abstract) + `SpawnerDataDto` / `RegionSpawnerDto` / `ProximitySpawnerDto`, each marked with a reusable `[JsonDiscoverableType]` opt-in attribute. Auto-discovered at the `Configure` phase — no manual registration list (avoids the regions `Register<T>()` footgun), open to custom spawner subtypes.
- **Symmetric mapping:** `BaseSpawner.ToDto()` (export) ⇄ `SpawnerDto.ToSpawner()` (import). `ToSpawner()` deletes-and-rethrows on any failure, so the importer can never orphan an Item.
- **`SpawnerJsonSerializer`** wires `$type` polymorphism on the `SpawnerDto` root with loud collision/constructibility validation.
- **Import/export commands** rewired to the typed DTO path (reflection `FindTypeByName`/`CreateInstance` removed).
- **Data migration:** the 109 `Distribution/Data/Spawns/**` files moved from `"type"`→`"$type"` and legacy `homeRange`→`spawnBounds`. The runtime still *reads* legacy `homeRange` for external files. The `homeRange→spawnBounds` formula is proven equivalent to the runtime conversion (`BoundsEquivalenceTests`, hr=0/1/3/7).
- **Deleted:** `Projects/Server/Json/DynamicJson.cs`.
Sparse export output matches the legacy `ToJson` (nullable DTO properties + `WhenWritingNull`). Binary world-save serialization is untouched.
## Tests
- DTO round-trip per spawner type; sparse-default omission; legacy `homeRange` read; export/import file round-trip.
- `Import_MalformedFile_LeaksNoWorldItems` — proves a mid-array parse failure constructs zero world Items.
- `AllSpawnFilesLoadTests` — every migrated spawn file deserializes and builds.
- Duplicate-discriminator validation.
- UOContent.Tests 485/485, Server.Tests 710/710, build clean.
## Follow-up (not in this PR)
`Rectangle3DConverter.Write` (in `Projects/Server/`) omits `z1/z2` when `Start.Z == -128`, so a future server-side export of a `homeRange`-style spawner round-trips depth 256→255. Pre-existing and out of scope here (Server change); the migrated data reads correctly. Worth a separate small converter PR.
### Summary
- Create BitMask256 struct with scalar operations (benchmarks showed AVX2 vectorization provides no benefit for this size)
- Refactor Map.cs to use BitMask256 for full Z range support (-128 to 127)
- Remove SectorSpawnCache struct, use BitMask256 directly in manager
- Update tests to use BitMask256 directly
- Remove unused test assertions for old 64-bit behavior
