fix(ci): run test projects on CI; remove brittle OPL attribute tests (#2513)

## Problem

Three coupled issues, each hiding the next:

1. **CI passed despite failing tests, with no test logs.** ([example run](https://github.com/modernuo/ModernUO/actions/runs/28639143286/job/84931544255) — the `Test` step produced zero output and the job went green.)
2. **Two `EmitsLowerStatReqWhenPassed` tests** fail with `KeyNotFoundException: '1060435'`.
3. Once CI actually ran the tests, **~337 UOContent tests failed** with `FileNotFoundException: tiledata.mul was not found` — the test bootstrap force-loaded copyrighted client data that CI doesn't have.

## Root causes & fixes

### 1. CI ran zero tests (`fix(ci)`)
The `Test` step ran `dotnet test --no-restore`, but the `Build` step only restores/builds `Application` — never the test projects. Without a restore, the test projects have no `project.assets.json`, so `Microsoft.NET.Test.Sdk`'s targets aren't imported, they aren't recognized as test projects, and `dotnet test` runs the `VSTest` target against **zero** projects → no output, **exit 0**.

- Both jobs now run `dotnet test --logger trx --results-directory ./TestResults` (test projects restore and run) **plus a guard** that fails the job if no `.trx` is produced — a permanent backstop against silent zero-test passes.

### 2. Impossible OPL tests (`fix(ci)` + `test(opl)`)
#2501 deliberately emits `LowerStatReq` (`1060435`) **inline in each item**, not in `GetProperties`. A follow-up "fix" dropped the `lowerStatReq:` argument to make the tests compile but left the assertions expecting `1060435`.

- Removed the two impossible tests, then removed the **entire `Tests/PropertyList/` OPL attribute set** from #2501: these assert exact cliloc/value/order of OPL emission per item base — a one-time proof of the #2501 rewire, now a permanent tax on modding (any admin reorder/value change/added line reddens the build). The one non-trivial case (LowerStatReq) is what just broke, because the test was wrong. Inline emission stays covered by the `BaseArmor`/`BaseClothing` tests.

### 3. Tile-data-dependent tests crashed CI (`test(uocontent)`)
UOContent.Tests' collection-fixture constructor force-loaded `tiledata.mul` unconditionally. On CI (no client files) it threw, and xUnit failed **every test in the collection** with the same error — mostly collateral (packet/scheduler/spawner tests that don't need tile data).

- Mirror Server.Tests' graceful pattern: `TestServerInitializer` probes for `tiledata.mul` and only loads tile/multi data (and runs the tile-dependent configure steps) when present, exposing `TileDataLoaded` so the fixture no longer throws.
- Add a shared `TileDataRequirement.SkipIfMissing()` guard and apply it to exactly the **31** pathfinding/multi/AI tests that genuinely need real tile data (`[SkippableFact]`/`[SkippableTheory]`).

## Verification (all local)

| Scenario | Server.Tests | UOContent.Tests |
|---|---|---|
| **Client data absent (CI)** | 726 pass, 17 skip, **0 fail** | 469 pass, 32 skip, **0 fail** |
| **Client data present (dev)** | 726 pass, 0 skip, **0 fail** | 501 pass, 0 skip, **0 fail** |

- Full `dotnet test` exits **0**; TRX files produced; the no-test guard trips (exit 1) only when zero `.trx` are produced.

Projects/UOContent.Tests/Fixtures/TestServerInitializer.cs

@@ -30,6 +30,13 @@ internal static class TestServerInitializer
     private static bool _initialized;
     private static readonly Lock _lock = new();
 
+    /// <summary>
+    /// True if the UO client tile data was found and loaded. When false (e.g. CI, where the
+    /// copyrighted client files are absent), tile/map/multi-dependent tests must skip rather than
+    /// fail. Guard such tests with <c>Skip.If(!TestServerInitializer.TileDataLoaded, ...)</c>.
+    /// </summary>
+    public static bool TileDataLoaded { get; private set; }
+
     public static void Initialize()
     {
         lock (_lock)
@@ -62,7 +69,10 @@ internal static class TestServerInitializer
             // flags are populated before anything that reads TileData (MultiData, MovementImpl,
             // CheckMovement). Without this, TileData.MaxItemValue is 0 at MultiData.Configure()
             // time, causing every MCL tile ID to be masked to 0 and stored as ID=0 in Tiles[x][y].
-            ForceLoadTileData();
+            // The copyrighted client files are absent on CI; when tiledata.mul is missing we skip
+            // the tile/map/multi-dependent bootstrap and leave TileDataLoaded false so those tests
+            // skip instead of failing the whole collection from the fixture constructor.
+            TileDataLoaded = TryForceLoadTileData();
 
             // Production runs every static Configure() via AssemblyHandler.Invoke("Configure");
             // the fixture calls a curated subset, so configure the pathfinding singleton here so
@@ -70,11 +80,15 @@ internal static class TestServerInitializer
             // calls Find. ServerConfiguration is already loaded above, so the setting resolves.
             BitmapAStarAlgorithm.Configure();
 
-            // Multi component lists (multi.mul / MultiCollection.uop). Production invokes this via
-            // AssemblyHandler.Invoke("Configure"); the curated fixture subset must call it so that
-            // BaseMulti.Components (MultiData.GetComponents) returns real footprints instead of
-            // MultiComponentList.Empty. Required by the Multi pathfinding tests.
-            MultiData.Configure();
+            if (TileDataLoaded)
+            {
+                // Multi component lists (multi.mul / MultiCollection.uop). Production invokes this via
+                // AssemblyHandler.Invoke("Configure"); the curated fixture subset must call it so that
+                // BaseMulti.Components (MultiData.GetComponents) returns real footprints instead of
+                // MultiComponentList.Empty. Required by the Multi pathfinding tests. Depends on the
+                // client files, so it only runs when tile data loaded.
+                MultiData.Configure();
+            }
 
             World.Configure();
             Timer.Init(0);
@@ -86,14 +100,23 @@ internal static class TestServerInitializer
             DecayScheduler.Configure();
             Server.Engines.Spawners.SpawnerJsonSerializer.Configure();
 
-            VerifyTrammelTileDataLoaded();
+            if (TileDataLoaded)
+            {
+                VerifyTrammelTileDataLoaded();
+            }
 
             _initialized = true;
         }
     }
 
-    private static void ForceLoadTileData()
+    private static bool TryForceLoadTileData()
     {
+        var tileDataPath = Core.FindDataFile("tiledata.mul", false);
+        if (string.IsNullOrEmpty(tileDataPath) || !File.Exists(tileDataPath))
+        {
+            return false;
+        }
+
         var loadMethod = typeof(TileData).GetMethod(
             "Load",
             BindingFlags.Static | BindingFlags.NonPublic
@@ -105,6 +128,7 @@ internal static class TestServerInitializer
             );
         }
         loadMethod.Invoke(null, null);
+        return true;
     }
 
     private static void VerifyTrammelTileDataLoaded()