`DragLocality.isSameBoard` resolved symlinks on both URLs, which stats every
path component. It ran five-plus times per `dropUpdated` and again per lane per
body evaluation through `renderedCards` → `hiddenMembers` — order of 50–100
stat calls per mouse-move, and worse on iCloud-backed paths. A pickup stall
sample had it on ~47 of 943 stacks.
`BoardRootKey` mints that canonical spelling once, where the root is, and every
locality comparison downstream is an `==` on two strings. The drag carriers hold
keys rather than URLs, so re-deriving under the cursor is no longer expressible.
`rootURL` keeps the user's spelling — the folder name is the display-name
fallback, and canonicalizing there would visibly rename a board opened through
a pin. The key follows the folder through `relocate(to:)`: a key frozen at open
would collide with a new board opened at the vacated path, and two boards
comparing as one is a cross-board drag silently behaving as a move.
Claude-Session: https://claude.ai/code/session_01CqjXB7ASoWtbyoGod68k97
rzen
ef423bb9d2