fix: keep Move to workspace submenu adjacent when flipped left

[le-immortal]

What this fixes

The Move to workspace submenu in the pane overflow menu rendered detached, far to the left of the menu, when the parent menu was right-aligned (panes on the right side of the grid).

Root cause

When the parent menu was anchored near the right edge of the viewport, the submenu was flipped to the left using a fixed SUBMENU_W = 240 width estimate (r.left - 4 - SUBMENU_W). Because that offset was based on a guessed width rather than the submenu's actual size, the submenu landed well to the left of the trigger row instead of beside it.

Fix

When flipping to the left, anchor the submenu's right edge against the trigger row's left edge (via a right style instead of a guessed left). The submenu now stays adjacent to Move to workspace regardless of its rendered width, with the same small 4px gap used on the right-side anchor.

Scope

Touches only the submenu positioning in TerminalPanel.tsx (state type + onClick anchor calc + render style). No behavioral change when the menu has room on the right.

[le-immortal]

uploaded image of after and before