Fix initial editor part size

[benibenj]

Copilot Generated Description: Adjust the initial size of the editor part to be half of the chat bar width upon its first appearance, ensuring it does not appear too small. Store the state to prevent resizing on subsequent show/hide cycles.

[Copilot]

Pull request overview

Adjusts the Agents (Sessions) window layout behavior so the editor part doesn’t appear overly narrow the first time it becomes visible in a workspace, and enforces a higher minimum width for the editor part to keep it usable.

Changes:

• Adds a workspace-scoped persisted flag to apply a one-time initial editor resize on first show.
• Implements _applyInitialEditorSize() to resize the editor to ~half of the available main-area width (with a 300px floor) and records that it ran.
• Increases the Sessions MainEditorPart minimum width to at least 300px.

Show a summary per file

File	Description
src/vs/sessions/browser/workbench.ts	Applies a one-time initial editor sizing when the editor part is first shown and persists a workspace flag to avoid repeating it.
src/vs/sessions/browser/parts/editorPart.ts	Enforces a 300px minimum width for the Sessions main editor part.

Copilot's findings

Comments suppressed due to low confidence (1)

src/vs/sessions/browser/workbench.ts:1691

• _applyInitialEditorSize() assumes the chat bar is visible and uses getViewSize(chatBarPartView).width. If the chat bar is hidden, getViewSize for that view is likely 0, which would make mainAreaWidth effectively just the current editor width and then shrink the editor to half of the available space on its first show. Consider skipping this initial resize when the chat bar is hidden (or basing the calculation on the actual available container width instead of the chat bar width).

		// initial split it would appear too small
		const mainAreaWidth = this.workbenchGrid.getViewSize(this.chatBarPartView).width + this.workbenchGrid.getViewSize(this.editorPartView).width;
		const targetEditorWidth = Math.max(300, Math.floor(mainAreaWidth / 2));
		const currentEditorSize = this.workbenchGrid.getViewSize(this.editorPartView);

• Files reviewed: 2/2 changed files
• Comments generated: 2