Fix layout-loading state regression in chat overlay projection

[google-labs-jules]

Problem:
During a rapid UI transition (like a session switch or hydration overlay), the XAML elements representing the active conversation root and the transcript surface could be destroyed and un-loaded because ShouldLoadActiveConversationRoot and ShouldLoadTranscriptSurface incorrectly reverted to false when their corresponding ShouldShow... properties were temporarily set to false.

Root Cause:
ChatConversationSurfaceProjectionCoordinator mapped the load states exactly 1:1 with the show states.

Why the fix is safe architecturally:
The fix changes the load states to be strict monotonic booleans per coordinator instance: once ShouldShow becomes true for the first time, ShouldLoad becomes and stays true. This preserves XAML performance (the tree is built once and hidden/shown, rather than torn down and rebuilt), aligns with standard Uno/WinUI practices for x:Load bindings, and keeps XAML state behavior purely within the Presentation.Core projection layer without touching the deeper domain or code-behind.

Exact verification commands I ran:

dotnet build SalmonEgg.sln --configuration Debug
dotnet test tests/SalmonEgg.Presentation.Core.Tests/SalmonEgg.Presentation.Core.Tests.csproj --configuration Debug --no-restore
dotnet test SalmonEgg.sln --configuration Debug --no-build

Any remaining unverified GUI-only risks:
No apparent GUI risks, as the visibility rules remain strictly data-driven via ShouldShow, and XAML bindings to x:Load will respect the persistent true state, maintaining local state on toggle. All ChatViewModel tests mapping derived states during rapid navigation switches passed successfully.

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PR created automatically by Jules for task 3281149794251732661 started by @YoungSx

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Project	Deployment	Actions	Updated (UTC)
salmonegg	Ready	Preview, Comment	Jun 3, 2026 10:59pm

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[YoungSx]

Closing during PR triage: this is a stale or duplicate layout-loading monotonicity attempt. #49 is the clean green candidate for this behavior; this PR is superseded, failing/conflicting, or mixed-scope and should not be merged as-is.

[google-labs-jules]

Closing during PR triage: this is a stale or duplicate layout-loading monotonicity attempt. #49 is the clean green candidate for this behavior; this PR is superseded, failing/conflicting, or mixed-scope and should not be merged as-is.

Understood. Acknowledging that this work is now obsolete and stopping work on this task.