fix(editor): stabilize selection menu sizing and transitions

[bajrangCoder]

No description provided.

[greptile-apps]

Greptile Summary

This PR stabilizes the touch-selection menu by deriving its dimensions from active content, resetting stale geometry, and coordinating primary/overflow transitions.

• Adds explicit overflow expansion state and cancellation-safe animation cleanup.
• Animates menu geometry and panel transitions from measured initial and final bounds.
• Updates selection-menu CSS for intrinsic sizing, hidden-panel removal, and bounded overflow layouts.

Confidence Score: 5/5

The PR appears safe to merge; no concrete blocking or independently actionable non-blocking issue remains.

The revised transition cancellation, expansion-state synchronization, rerender cleanup, and overflow sizing remain internally consistent across opening, rapid reversal, rerender, and close paths.

Important Files Changed

Filename	Overview
src/cm/touchSelectionMenu.js	Reworks overflow transition state, geometry measurement, cancellation, and lifecycle cleanup without an identified actionable defect.
src/main.scss	Replaces fixed menu sizing with content-driven dimensions and preserves bounded scrolling for overflow actions.

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