Persist sessions sidebar section collapse state

[daviddossett]

Persists the expanded/collapsed state of timestamped sections (Today, Yesterday, Last 7 days, etc.) in the sessions sidebar across view open/close and restarts.

Changes:

• Added IStorageService to AgentSessionsControl to persist section collapse state
• Section collapse/expand is saved to profile-scoped storage whenever the user toggles a section
• On initial render, saved state is checked before falling back to default collapse logic
• Listens to the tree's onDidChangeCollapseState event, unwrapping the IAsyncDataTreeNode to access the actual section element

[Copilot]

Pull request overview

This PR adds persistence for the expanded/collapsed state of timestamped sections in the Agent Sessions sidebar by storing section collapse state in profile-scoped storage and restoring it on render.

Changes:

• Injects IStorageService into AgentSessionsControl and adds helpers to read/write persisted section collapse state.
• Updates collapseByDefault to consult persisted state before applying the existing default collapse rules.
• Listens to the tree’s onDidChangeCollapseState and saves the new state (unwrapping IAsyncDataTreeNode to access the underlying section element).

Comments suppressed due to low confidence (1)

src/vs/workbench/contrib/chat/browser/agentSessions/agentSessionsControl.ts:223

• The comments describing default behavior (e.g. “More section is always collapsed…”, “Archived section is collapsed…”) are no longer strictly true once persisted collapse state takes precedence. Please update these comments to reflect that they only apply when there is no saved user preference.

				if (element.section === AgentSessionSection.More && !this.options.filter.getExcludes().read) {
					return true; // More section is always collapsed unless only showing unread
				}
				if (element.section === AgentSessionSection.Archived && this.options.filter.getExcludes().archived) {
					return true; // Archived section is collapsed when archived are excluded
				}

[bpasero]

@daviddossett some feedback:

• this is quite a significant change for us releasing this to 40m users shortly after (today is testing day!)
• I see no associated issue to test this and verify it
• I would have appreciated a ping to review the change as I have been working on this area mainly and thought about this too in the past

Zurich has been holding back larger changes today to stabilise, I feel this change should be reverted and then properly put in for another release. Thoughts?

cc @jo-oikawa @lostintangent @jrieken @benvillalobos

[daviddossett]

Reverting—it felt like a small change for me but apologies for pushing through during testing.