feat(web): make left column width adjustable by codex

[yzs981130]

Motivation

• Ensure user-resized sessions sidebar width.

Description

• Added state and refs (sidebarWidth, sidebarWidthRef, isDraggingSidebar) to manage size.
• Consolidated width clamping, state update, and localStorage persistence into a single updateSidebarWidth helper and used it for pointer drag and resize-reclamp actions.

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Codex Task

[github-actions]

[MINOR] [PERF] localStorage write on every pointermove

Why this is a problem: pointermove fires at high frequency; localStorage.setItem is synchronous and can block the main thread, making the resize feel janky on lower-end devices. This path runs on every drag tick.

Suggested fix:

const updateSidebarWidth = useCallback((nextWidth: number) => {
    const clamped = clampSidebarWidth(nextWidth)
    if (sidebarWidthRef.current === clamped) return
    sidebarWidthRef.current = clamped
    setSidebarWidth(clamped)
}, [clampSidebarWidth])

const persistSidebarWidth = useCallback(() => {
    if (typeof window !== 'undefined' && sidebarWidthRef.current != null) {
        window.localStorage.setItem(SIDEBAR_WIDTH_STORAGE_KEY, String(sidebarWidthRef.current))
    }
}, [])

const handlePointerUp = () => {
    persistSidebarWidth()
    setIsDraggingSidebar(false)
}

[github-actions]

Findings

• [Minor] Synchronous localStorage.setItem on every pointermove may cause resize jank; consider persisting on pointerup or debouncing web/src/router.tsx:129

Summary

• 1 minor perf issue. Residual risk: drag feels sluggish on low-end devices if left as-is.

Testing

• Not run (automation)