## 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
* Upgrades Serialization Generator to v3. This contains numerous bug fixes and a significant performance improvement.
* Bumps other dependencies.
### Summary
* Bumps to .NET 9 with updated dependencies
* Comparing a value type against null is no longer allowed
* CI/CD now uses the version specified in global.json
* Serialization generator updated to .NET 9 with bug fixes, fixes to turkish language, and parallelization
> [!Note]
> **Developer Note**
> Now developers will only need to build/run the Application project instead of everything.
> When adding new projects, make sure to:
> 1. Add a reference to that project in the Application project.
> 2. Add the dll file to the Distribution/Data/assemblies.json file
### Summary
- Adds an application project
- Consolidates process restarts to use `Core.Kill(true)`
- Removes some old messaging, for example processor optimization
- Fixes missing build cleanup
