NSToolbar through the existing HostedWindowController rather than
SwiftUI's toolbar — for reasons that are contract, not taste: 03's
transient-search clause is a decision over the toolbar's current
contents, which NSToolbar publishes and SwiftUI's API cannot answer;
Undo/Redo are the system's nil-target responder-chain actions so the
toolbar items validate exactly as the menu rows do (disabled on base
boards, alive in m8 unchanged); and the search item hosts the real
NSSearchField with explicit first-responder control. Customization is
all system furniture — Customize sheet, drag rearrange, display-mode
popup, overflow, autosaved per window kind. Board default: the search
field alone, trailing; catalog adds New Card, New Lane, Undo, Redo,
Show Trash, every action extracted from its menu command so no second
predicate exists. Card default: the Edit Body / Raw Source toggles and
Add Attachment, mirroring their commands' own predicates live via
observation tracking. Removing the search item keeps the promise —
⌘F surfaces the same field as a transient strip under the title bar,
persisting until the query clears, and an overflowed item that cannot
take the keyboard falls through to the strip too.
Claude-Session: https://claude.ai/code/session_01SR4XGjmBE16ZUYWpfFHXwY
