fix(ui): stop task cards teleporting when a sidebar toggles

[Limdongcheng]

Root cause

fit_layout translated a card rigidly with its anchored boundary's displacement: hiding the secondary sidebar teleported every right-anchored card by the full sidebar width even when the card was parked mid-board, and the user then had to drag it all the way back. Drag origins were taken from the stored layout rect, which no longer matched what was on screen — the first stretch of a drag was spent "catching up" the discrepancy.

Fix

CardLayout now keeps the user-intended rectangle (preferred) separate from the fitted one:

• Only an edge actually resting on a boundary follows that boundary (the default top-right docking).
• A parked card keeps its absolute position and is merely clamped inside the new bounds.
• A card a sidebar pushed aside returns to its place once the boundary recedes.
• Drag and resize gestures write both rectangles, so drag origins always match the rendered position.

Tests

A full-render regression test drives sidebars, workspace geometry and the Processing card through a hide/drag sequence; fit-level tests pin the parked-stays-put and displaced-returns semantics. cargo pr-check passes.

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Part 1 of a 6-PR stack (task-card geometry → clickable affordance → H/F fits → peak snap → peaks follow reference → reference on-plot pick).

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