fix(chat): ensure layout loading states are monotonic during lifecycle overlays

[google-labs-jules]

The Observed Problem

When navigating or switching sessions, temporary blocking overlays (like the session switch or history loading overlay) cause the chat components to temporarily evaluate ShouldShowActiveConversationRoot and ShouldShowTranscriptSurface to false. Because ShouldLoad... properties were directly mirroring ShouldShow..., this caused the underlying layout items (bound to x:Load) to be completely unloaded and destroyed. When the overlay cleared, the visual tree had to be expensively reconstructed, causing UI stutter and violating the layout realization contract.

The Root Cause

In ChatConversationSurfaceProjectionCoordinator, the projection blindly mapped ShouldShow states directly to ShouldLoad states:

state.ShouldShowActiveConversationRoot, // mapped to ShouldLoadActiveConversationRoot
...

This violates the Uno Platform best practice and repository AGENTS.md rules which state: "In the Uno Platform UI lifecycle, separate layout realization (ShouldLoad... properties typically bound to x:Load) from visual state visibility (ShouldShow... properties). Layout-loading states should be monotonic and not regress (un-load) merely because a temporary blocking overlay becomes visible."

Why the Fix is Safe Architecturally

The fix simply introduces internal boolean tracking (_hasLoadedActiveConversationRoot, _hasLoadedTranscriptSurface) within the ChatConversationSurfaceProjectionCoordinator. Once the layout evaluates that it needs to be shown (and thus loaded), the ShouldLoad projection permanently returns true for the lifecycle of that coordinator instance.

1. It does not touch ShouldShow... logic, so the UI is still correctly hidden/collapsed when overlays appear.
2. It adheres to Uno Platform x:Load patterns: once loaded, it stays in the visual tree and visibility is controlled independently.
3. It prevents native visual tree thrashing without moving any business logic into the view.
4. It is fully covered by updated unit tests in ChatConversationSurfaceProjectionCoordinatorTests.

Exact Verification Commands Run

• dotnet build SalmonEgg.sln --configuration Debug
• dotnet test tests/SalmonEgg.Presentation.Core.Tests/SalmonEgg.Presentation.Core.Tests.csproj --configuration Debug --no-restore (Note: Tested specifically the ChatConversationSurfaceProjectionCoordinatorTests and ChatViewModelTests to ensure our changes passed)

Any Remaining Unverified GUI-only Risks

• The fix prevents the unloading of the transcript and active conversation root. If there are any custom native behaviors in the controls that rely implicitly on being destroyed and recreated (which is an anti-pattern), they could technically behave differently now. A full GUI smoke test covering repeated rapid session switching under heavy memory load would be ideal to ensure the retained visual tree performs smoothly without leaks.

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PR created automatically by Jules for task 15362945017983675042 started by @YoungSx

[google-labs-jules]

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Project	Deployment	Actions	Updated (UTC)
salmonegg	Ready	Preview, Comment	Jun 12, 2026 1:16am

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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.