fix(layout): fix visual flicker in sidebar on collapse

[janburzinski]

before:
https://streamable.com/tqiq62

after:
https://streamable.com/af1tj5

[greptile-apps]

Greptile Summary

This PR eliminates the sidebar collapse flicker by eagerly updating isLeftOpen state before triggering programmatic collapse/expand, and blocking intermediate onResize events during the animation via the existing panelDragStore suppression window.

• setCollapsed now calls setIsLeftOpen(!collapsed) eagerly before panel.collapse()/panel.expand(), so the React state reflects the intended outcome immediately rather than waiting for the panel library to emit its final resize event.
• syncLeftOpenFromPanel replaces the former inline setIsLeftOpen callback on onResize, short-circuiting when getIsSuppressing() is true so the 140 ms burst of intermediate events cannot overwrite the eagerly-set state.
• panelDragStore gains a getIsSuppressing() accessor to expose the suppression flag for synchronous reads outside of useSyncExternalStore.

Confidence Score: 5/5

Safe to merge — the changes are narrowly scoped to the sidebar collapse path and the logic correctly prevents state from being overwritten during animation.

The eager setIsLeftOpen update combined with the suppression guard directly eliminates the flicker root cause. No new state paths are introduced that could regress other behaviour, and the panelDragStore addition is a read-only accessor with no side effects.

No files require special attention.

Important Files Changed

Filename	Overview
src/renderer/lib/layout/layout-provider.tsx	Core fix: eager setIsLeftOpen(!collapsed) before panel API call, plus syncLeftOpenFromPanel that guards against suppression window — logic is sound and context interface is correctly updated.
src/renderer/lib/layout/panel-drag-store.ts	Minimal, correct addition of getIsSuppressing() as a synchronous read accessor alongside the existing useSyncExternalStore-compatible API.
src/renderer/lib/layout/workspace-layout.tsx	One-line change swapping the inline onResize callback for syncLeftOpenFromPanel; no other logic touched.

Sequence Diagram

sequenceDiagram
    participant User
    participant toggleLeft
    participant setCollapsed
    participant panelDragStore
    participant ReactState
    participant panel as react-resizable-panels
    participant syncLeftOpenFromPanel

    User->>toggleLeft: cmd+B / click
    toggleLeft->>setCollapsed: setCollapsed('left', true)
    setCollapsed->>panelDragStore: suppressFor(140ms)
    setCollapsed->>ReactState: setIsLeftOpen(false) [eager]
    setCollapsed->>panel: panel.collapse()

    loop onResize burst (0-140ms)
        panel-->>syncLeftOpenFromPanel: onResize fires
        syncLeftOpenFromPanel->>panelDragStore: getIsSuppressing()
        panelDragStore-->>syncLeftOpenFromPanel: true - early return
    end

    Note over panelDragStore: 140ms timer expires
    panelDragStore->>panelDragStore: "isSuppressing = false"

    panel-->>syncLeftOpenFromPanel: final onResize (if any)
    syncLeftOpenFromPanel->>panelDragStore: getIsSuppressing()
    panelDragStore-->>syncLeftOpenFromPanel: false
    syncLeftOpenFromPanel->>ReactState: "setIsLeftOpen(!isCollapsed()) = false"

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_{Reviews (2): Last reviewed commit: "fix(layout): ignore suppressed sidebar r..." | Re-trigger Greptile}

[janburzinski]

@greptileai