bug(desktop): split view right pane does not resize when expanding the left pane

[i-trytoohard]

Bug

When resizing the split view by expanding the left pane (terminal), the right pane (documentation/preview) remains fixed at its previous width instead of resizing to fit the remaining available space. This causes the layout to break — leaving unused or overlapping space.

Steps to Reproduce

1. Open the application in split view.
2. Ensure both the left terminal pane and the right documentation/preview pane are visible.
3. Drag the divider to expand the left pane.
4. Observe the right pane.

Expected Behavior

• The right pane should dynamically resize as the left pane expands.
• Both panes should remain responsive and share the available width.

Actual Behavior

• The left pane expands normally.
• The right pane remains stuck at its previous width instead of resizing.
• The layout appears broken, leaving unused or overlapping space.

Environment

• OS: Fedora Linux
• Browser: Firefox

Reported by

@Kzark (Discord)

Likely Related

• fix(browser): clip preview view to its panel column so it can't render out of bounds #2203 — fix(browser): clip preview view to its panel column so it can't render out of bounds. This PR fixed the native WebContentsView spilling out of bounds, but the ResizeObserver + flex-grow animation interaction is fragile. If the right pane is a WebContentsView, expanding the left pane may not trigger a re-measure, leaving the right pane stale.
• (WEB) : Session detail page should use fixed split layout instead of page scrolling on desktop #1246 — Established the fixed split-pane layout.
• bug(desktop): sidebar cannot fully expand/collapse from resized near-collapsed state #2424 — Sidebar resize handle trapping UI in intermediate states.

[somewherelostt]

Thanks for contributing to Agent Orchestrator.

This issue is being picked up by the current external contributor on-call pair:

• @neversettle17-101
• @somewherelostt

If someone is already working on this, please continue as usual.
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[xuelongmu]

A focused downstream implementation has landed and is available for upstream replay: xuelongmu#203 (squash 43c84ce; exact behavior head 0b989a8). It exposes a stable BrowserView remeasure action and invokes it from the inspector panel's resize callback, so the native overlay receives current bounds during divider geometry changes even when the slot ResizeObserver does not fire. Focused tests cover both the SessionView trigger and delivery of fresh coordinates; exact head passed all 3 frontend/format/gitleaks checks, had zero review threads, received a clean exact-head GitHub Codex verdict, and an independent Sol/xhigh audit found P0/P1/P2=0. Issue state is unchanged.