`HostedWindowController.hideTitle()` was the same shape of bug a429a7e fixed for
`titlebarAppearsTransparent`: an out-of-band `NSWindow.titleVisibility` write, correct the
instant it ran, undone by SwiftUI's own next pass over the window's configuration — a tree
that declares nothing resolves `.visible`, and SwiftUI writes that back over the out-of-band
`.hidden` on the very next `@State`-driven re-render this board window's own liveness causes.
The system title reappeared beside the board-popover widget, "occasionally" — whenever that
next re-render happened to land.
Confirmed with an A/B harness (no interactive display in this session, so not reproduced on
screen; mechanism established in code, per the card's own fallback): a bare out-of-band write
held indefinitely against resize and key-status changes alone, but reverted on the very next
`@State`-driven render and stayed reverted — reasserting from `body`'s own construction or
from `.onChange` both lost the same race, since SwiftUI's resync runs later than either. The
only thing that held was declaring the posture in the tree itself, mirroring
`.toolbarBackgroundVisibility`'s role in a429a7e.
`KanbanApp`'s board `WindowGroup` now declares `.windowToolbarStyle(.unified(showsTitle:
false))`. It is a scene modifier, not a per-window one, so — unlike `.toolbarBackgroundVisibility`
— it cannot wait for a board's load to finish before taking effect; every board window it
creates keeps the system title hidden from its very first frame. `boardLoadingTitlebarAccessory`
covers the gap that opens before the loading window has a store to build the real widget from: a
small, non-interactive, plain-text stand-in carrying the registry record's cached name, installed
the moment the window attaches and swapped by identity for the real widget the moment the store
loads — so the loading window's chrome still carries a name throughout, per 02-architecture.md.
`hideTitle()`'s own write stays; it is no longer what keeps the title hidden, but it is still
correct for the one render turn before the scene's own re-assertion catches up.
Confined to `BoardWindowHost.swift`, `BoardInfoPopover.swift` and `KanbanApp.swift` —
`WindowAccessor.swift`'s shared `hideTitle()`/`titleVisibility` machinery is untouched, since a
concurrent fix is addressing the card window's version of this same bug through that file.
New regression tests (`BoardLoadingTitlebarStandInTests`, `KanbanTests/BoardLoadingTests.swift`)
pin the stand-in's layout and the identity-based swap. Full suite green (3219 tests) except the
pre-existing, documented environment-sensitive `PointerLatencyTests`, confirmed unaffected by
rerunning them in isolation.
Claude-Session: https://claude.ai/code/session_014PtZdPwqZuqEDLc6wZMtEy
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