fix(app): keep the first sidebar section open across pages

[slyk]

Change description

Part of discussion #431 (item 2.3).

When the sidebar is open, it automatically expands its first section (usually "Information"). But after navigating to another page, the sidebar stays open with every section collapsed, so it shows nothing useful until the user clicks a section.

Cause: sidebar-detail-group.vue only opens the first section in a watcher on sidebarOpen changes. Each page mounts a new private-view while sidebarOpen (persisted in local storage) is already true, so the watcher never fires.

Fix:

• The group also opens the first section when it mounts with the sidebar open.
• It does so without the expand animation, so the section is simply shown open on page load.
• The new disabled prop on transition-expand switches the transition off: no CSS classes, no JS hooks.
• It is turned off only for that first render; opening the sidebar by hand still animates as before.

Type of change

• Bug fix (fixes an issue)
• New feature (adds functionality)

Related issues

Discussion #431

Checklists

Development

• Lint rules pass locally
• Application changes have been tested thoroughly
• Automated tests covering modified code pass

Security

• Security impact of change has been considered: none, UI state only.
• Code follows company security practices and guidelines

Network

• Changes to network configurations have been reviewed (not applicable)
• Any newly exposed public endpoints or data have gone through security review (not applicable)

Code review

• Pull request has a descriptive title and context useful to a reviewer. Screenshots or screencasts are attached as
  necessary
• reviewers assigned
• Pull request linked to task tracker where applicable