fix(time): retail-canonical month enum + absolute Portal Year + title-bar calendar

Two bugs in calendar display (the CLOCK ITSELF was already correct):

1. **Month enum had wrong order + non-retail names.** Old enum:
   Snowreap=0, ColdMeet, Leafdawning, Seedsow, Rosetide, Solclaim, ...
   At day-of-year 83 this gave month index 2 = Leafdawning. Retail's
   @timestamp at the same moment shows "Seedsow 24". Fixed enum to
   chronological order starting at year-anchor month Morningthaw, with
   retail-canonical names:
     Morningthaw=0, Solclaim, Seedsow, Leafdawning, Verdantine,
     Thistledown, Harvestgain, Leafcull, Frostfell, Snowreap,
     Coldeve, Wintersebb.
   At day-of-year 83 → month 2 = Seedsow ✓

2. **ToCalendar returned relative year, not absolute Portal Year.**
   We had AbsoluteYear() = relative_year + ZeroYear (=10) but
   ToCalendar's Calendar.Year was the relative one. So acdream's
   title bar showed "PY 106" while retail's @timestamp at the same
   tick showed "PY 116". Fixed ToCalendar to add ZeroYear so the
   exposed Calendar.Year matches retail's display.

3. **GameWindow title bar now shows the calendar.** Format mirrors
   retail's @timestamp output:
     "PY<Year> <Month> <Day> <Hour> (df=<dayFraction>)"
   Lets the user read the same fields off both clients and confirm
   clock parity directly. Drift > 1 hour = real bug.

Tests:
- Updated ToCalendar_PY10Day1_Morningthaw (renamed from PY0Day1_Snowreap)
- Updated ToCalendar_AdvancesCorrectly (Snowreap→Morningthaw etc.)
- Added regression: ToCalendar_TickAtSeedsow24Year106_MatchesRetailFormat
  pinning a retail-known tick → retail-known calendar string.

The dayFraction formula (CalcDayBegin's `arg2 + zero_time_of_year`,
decomp 0x005a6400 line 434549) was already correct; an earlier-this-
session attempt to flip the sign was reverted in this same commit's
parent. The "few minutes drift" observed in dual-client comparisons
this session was a combination of:
  - calendar label mismatch (this fix addresses)
  - slot-boundary rounding (fixes itself)
  - 1-minute wall-clock interpolation drift (within tolerance)

NOT a clock-formula bug. ISSUE #3 in docs/ISSUES.md is now misnamed
("Client clock drifts from retail"); plan to re-title or close in a
follow-up commit after the visual-divergence investigation lands.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

src/AcDream.App/Rendering/GameWindow.cs

@@ -4565,9 +4565,18 @@ public sealed class GameWindow : IDisposable
             int entityCount = _worldState.Entities.Count;
             int animatedCount = _animatedEntities.Count;
 
-            _window!.Title = $"acdream | {fps:F0} fps | {avgFrameTime:F1} ms | " +
-                             $"lb {visibleLandblocks}/{totalLandblocks} visible | " +
-                             $"ent {entityCount} | anim {animatedCount}";
+            // Calendar display matches retail's @timestamp output:
+            // "Date: <Month> <Day>, PY <Year>  Time: <HourName>".
+            // Use NowTicks (server-synced + wall-clock interpolation) so the
+            // user can read the same fields off both acdream and retail and
+            // confirm clock parity directly. Drift > 1 hour = real bug.
+            double tNow = WorldTime.NowTicks;
+            var titleCal = AcDream.Core.World.DerethDateTime.ToCalendar(tNow);
+            double df = WorldTime.DayFraction;
+            _window!.Title =
+                $"acdream | {fps:F0} fps | {avgFrameTime:F1} ms | " +
+                $"lb {visibleLandblocks}/{totalLandblocks} | ent {entityCount}/anim {animatedCount} | " +
+                $"PY{titleCal.Year} {titleCal.Month} {titleCal.Day} {titleCal.Hour} (df={df:F4})";
             _lastFps = fps;
             _lastFrameMs = avgFrameTime;
             _perfAccum = 0;