fix(web): restore composer controls as space becomes available#9539

Note

Low Risk Localized layout hysteresis logic for the resting composer footer with added regression tests; no auth, data, or API changes.

Overview Fixes resting composer footer controls staying fully overflowed when only the last block still needs the 1px anti-oscillation slack.

resolveRestingComposerControlsLayout no longer snaps back to the previous hiddenCount in one step when shrinking the overflow menu. It now walks hiddenCount upward until the layout fits within hostWidth - RESTING_CONTROLS_SLACK_PX or matches the prior hidden count, so controls that fit (e.g. one of two blocks at 357px) come back inline while the rest stay in overflow until there is slack.

New hysteresis tests cover partial restoration, exact-threshold retention, and stability across re-layout passes.

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Note

Fix resolveRestingComposerControlsLayout to restore composer controls one block at a time

• Replaces the single-step hysteresis fallback with a loop that advances the hidden count one block at a time until the candidate layout fits with the configured slack.
• Previously, when controls were hidden and the fully restored candidate lacked slack, the resolver reverted to the previous hidden count. Now it retains the greatest number of restored blocks that fit.
• Adds tests for partial multi-block restoration, stability at the same width, and the one-pixel slack boundary at the minimum threshold.
• Risk: resolveRestingComposerControlsLayout in composerFooterLayout.ts changes restoration behavior; layouts that relied on all-or-nothing restoration may now show partially restored controls.

^{Macroscope summarized 4268800.}