ci: tag DAT-dependent tests into the InstalledDat lane; drop invariant workaround

Three tests reached the CI gate needing the installed retail DATs, which no
build machine has, and failed with FileNotFoundException on client_cell_1.dat:
  - Issue127FloodFlipReplayTests (both facts replay via ResolveDatDir)
  - FindCellListConformanceTests.FindCellList_DoorwayThreshold_IndoorPicks_
    MatchRetail, the one untagged method among already-tagged siblings
They now carry [Trait("Lane", "InstalledDat")] like every other DAT test, so
the gate filter excludes them and the local DAT lane still runs them.

Also reverts the DOTNET_SYSTEM_GLOBALIZATION_INVARIANT pin from the previous
commit. It was too blunt: it fixed the 40 decimal-comma failures but broke
ChatLogTests.FormatTimestampPrefix_UsesLiteralColons_RegardlessOfCurrentCulture,
which legitimately constructs a culture and cannot under invariant mode. The
runner's HKCU locale (LocaleName=en-SE, sDecimal=',') was corrected to en-US
instead, which is the actual defect.

.gitea/workflows/ci.yml

@@ -41,15 +41,6 @@ jobs:
 
       - name: Test (lane-filtered, streaming)
         shell: pwsh
-        env:
-          # The gate must not depend on the runner's regional settings. This
-          # box reports en-US interactively but the scheduled task inherits
-          # en-SE (English/Sweden, COMMA decimal separator), which broke 40
-          # tests across four projects on formatted numbers alone —
-          # e.g. expected "update:0.25", got "update:0,25". Set-Culture does
-          # not reach a task that runs without loading the user profile, so
-          # pin globalization for the test processes instead.
-          DOTNET_SYSTEM_GLOBALIZATION_INVARIANT: '1'
         run: |
           $ErrorActionPreference = 'Stop'
           $filter = 'Lane!=InstalledDat&Lane!=PreparedPackage&Lane!=Live&Lane!=Manual&Lane!=Windows&Lane!=Linux&Lane!=SystemFont&Purpose!=Diagnostic&Status!=KnownFailure'

tests/AcDream.App.Tests/Rendering/Issue127FloodFlipReplayTests.cs

@@ -30,6 +30,7 @@ namespace AcDream.App.Tests.Rendering;
 /// bistable admission, and the bisect along the eye segment names the knife
 /// edge.
 /// </summary>
+[Trait("Lane", "InstalledDat")]
 public class Issue127FloodFlipReplayTests
 {
     private readonly ITestOutputHelper _out;

tests/AcDream.Core.Tests/Conformance/FindCellListConformanceTests.cs

@@ -130,6 +130,7 @@ public class FindCellListConformanceTests
     /// separate outdoor-entry validation.
     /// </summary>
     [Fact]
+    [Trait("Lane", "InstalledDat")]
     public void FindCellList_DoorwayThreshold_IndoorPicks_MatchRetail()
     {
         var (cache, picks) = LoadThresholdGolden();