## Summary
Adopts ModernUO.Serialization 4.0.0 across the engine. Three commits, reviewable independently:
1. **Package + tool bump to 4.0.0** (`Server.csproj`, `UOContent.csproj`, `dotnet-tools.json`).
2. **Timers → `[DeserializeTimer]`** — the 8 drifting timers (BaseLight, TreasureMapChest, MarkContainer, FillableContainer, DeathRobe, DecayedCorpse, Corpse, BaseEscortable) now store their next tick as **anchored time**: server downtime no longer consumes the remaining delay, and idle-world saves are byte-stable. This changes their wire format, so each class bumps its serialization version with a `MigrateFrom` that replays the old delta-time read through the migration schema (the new `vN.json` files carry `@AnchoredTimer`; the old ones keep `@TimerDrift`, which the generator reads forever). The 2 wall-clock timers (Aquarium, FountainOfLife) keep their exact format via `wallClock: true` — no bump. Restart methods drop their `TimeSpan.MinValue` sentinel checks: v4 invokes them **only when a timer was actually running at save**.
3. **Linkage → field-side declarations** — 175 conversions across 25 files: `[SerializableFieldSaveFlag(order)]`/`[SerializableFieldDefault(order)]` become `[SaveFlag(nameof(...), nameof(...))]` on the field, and `[SerializableFieldChanged(order)]` becomes the `fieldChanged:` argument of `[SerializableField]`. **Wire-neutral: zero migration schemas changed.**
## Verification
- Solution builds with **0 errors, 0 warnings**; all three 4.0.0 packages verified indexed on nuget.org (no local feed needed).
- **835 + 708 tests green.**
- Generated output inspected: old-version content structs replay `ReadDeltaTime` (e.g. `V3Content.DecayTimerNext = reader.ReadDeltaTime()`), current versions write/read anchored time with the gated restart, and the wall-clock classes emit byte-identical `Write`/`ReadDateTime` framing.
- Schema tool run is committed (CI's `git diff --exit-code` schema check passes): exactly the 8 expected new `vN.json` files, nothing else touched.
- The conversion was scripted with a class-scoped resolver (order → same-class `[SerializableField(order)]`/`[SerializableProperty(order)]`); it planned 175/175 with zero ambiguities before applying.
## Notes
- New `MigrateFrom`s use the content structs' provided `XxxDelay` property, matching the pre-existing idiom in Corpse's and TreasureMapChest's older migrations.
- Follow-up candidate (separate PR, wire-neutral, any time): fold the ~150 eligible hand-written `[SerializableProperty]` setters (clamps, post-change side effects) down to `[SerializableField]` with `allowFieldChange`/`fieldChanged` hooks.
### Summary
* Makes mount stamina significantly faster.
* Reduces absolute reset from 24 hours to 4 hours.
* Adds Pub 46+ Ethereal stamina where the stamina is global to all mounts for the player
* Removes serialization of stamina entirely because it's ok if it gets reset during shard restarts.
## Overhaul to Stamina (Overweight) System
### Added configurations
```json
{
"settings": {
"stamina.enableMountStamina": "True",
"stamina.cannotMoveWhenFatigued": "True",
"stamina.stonesPerOverweightLoss": "25",
"stamina.stonesOverweightAllowance": "4",
"stamina.baseOverweightLoss": "5",
"stamina.additionalLossWhenBelow": "0.1",
"stamina.mountLastMoveStepsReset": "01:00:00:00",
"stamina.enableMountStamina": "True",
"stamina.useMountStaminaOnlyWhenOverloaded": "False",
},
}
```
- `stamina.cannotMoveWhenFatigued` - By default, Pre-AOS expansions will outright block a player if they are fatigued. A player is fatigued when they run out of stamina by any mechanism.
- `stamina.stonesPerOverweightLoss` - The amount of stamina lost for every X stones above overweight. Example, if a person is overweight 28 stones overweight, then there there is 1 additional stamina. 28 / 25 = 1 (no decimals, no rounding)
- `stamina.stonesOverweightAllowance` - The number of stones allowed before overweight penalties take affect. This _does not_ substract from the overweight stones calculation.
- `stamina.baseOverweightLoss` - The base amount of stamina loss for being overweight. While running, the final amount is multiplied by 2. If mount stamina is turned off, then the final amount is divided by 3 while mounted.
### Mount stamina
Mounts have a new property `StepsMax` to determine the maximum steps they can take before being fatigued. To regain steps, the player _must stay on the mount and not move_ (per OSI). The gain rates are configurable. If a mount is dismounted, or the player logs off, the mount is considered inactive and mounts regain all of their steps after _24 hours_.
### Changes to player stamina
Players now have a proper inactivity time reset for their steps. If a player is idle for 16 seconds (including logging off, or the server being offline), then the steps counter is rest.
### Developer Notes
- `StepsTaken` - This field has been removed. It was not serialized and could not be used reliably. If a developer was using it, then the recommendation is to build a mechanism to track total steps another way.
- `IHasStamina` - This new interface was added and currently `IMount` and `PlayerMobile` are valid types.
Important: Entities that are sent to the StaminaSystem for tracking (mounts, players, or something else), must be an `ISerializable` to be serialized properly. If they are not, then the serialization system will record a null, and nothing will be deserialized upon world load. No errors will be given.
## Breaking Changes (New API)
ObjectPropertyList supports the following API:
```cs
list.Add(500000);
list.Add(500001, stringArgument);
list.Add("Some text");
list.Add($"Some text with {argument}");
list.Add(500002, $"{arg1}\t{arg2}");
```
## Notes
1. All API uses that require a formatter like this:
```cs
list.Add(500002, "{0}\t{1}", arg1, arg2);
```
Should be changed to use string interpolation, for example:
```cs
list.Add(500002, $"{arg1}\t{arg2}");
```
2. The following paradigm should no longer be used:
```cs
list.Add(1061170, prop.ToString()); // strength requirement ~1_val~
```
The new string interpolation API will avoid having to convert the argument to a string before writing it to the packet. Instead use the following:
```cs
list.Add(1061170, $"{prop}"); // strength requirement ~1_val~
```
### Benchmarks
```cs
| Method | Mean | Error | StdDev | Gen 0 | Allocated |
|------------------------------- |---------:|--------:|--------:|-------:|----------:|
| BenchmarkOldOPL | 241.0 ns | 0.56 ns | 0.47 ns | 0.0105 | 88 B |
| BenchmarkStringInterpolatedOPL | 199.9 ns | 2.44 ns | 2.39 ns | - | - |
```
### Changes
- [X] Removes crash in STArray.Return when array is null.
- [X] Fixes NPE in OPL when entity is null. Serial in packet will be 0 when entity is null.
- [X] Fixes NPE in AosAttributes when Parent is null.
- [X] Changes OPL to use string interpolation.
- [X] Introduces `IPropertyList` to allow extending PropertyList for other uses.
- [X] Fixes an issue where a buffer smaller than 8 bytes would not double with enough space in some cases.
- [X] Fixes an issue with dupe copying the savebuffer reference (ugh).
- [X] Streamlines the IGenericWriter API to use better generics.
- [X] Streamlines the IGenericReader API to use better generics.
- [X] Forces `tidying` of a List/HashSet to be done externally since Writers/Readers should not have side effects.
- [X] Fixes an issue where Tidying a list didn't TrimExcess, causing memory leaks.
- [X] Reverted the meaning of `World.Running` to specifically refer to any world state post world loading.
- NOTE: Do not use this if you want to block on world saves. Instead use checks against `WorldState.Saving` states.
- [X] Fixes an issue with serializing negative DateTime deltas.
- [X] Fixes a potential issue with serializing non-UTC DateTime.
Bumps release version
- [X] Fixes several bugs
- [X] Updates more ordinal issues
- [X] Cleans up the code a bit
- [X] Turns classes static that should have been
- [X] Changes TcpServer.Instances to a HashSet
Bumps release version
