🤖 fix: focus main region after sidebar collapse

[tracyjohnsonux]

Summary

Focus the active route's main region after a sidebar collapse so keyboard input is not left on the collapsed rail button. Workspace, project creation, and scratch routes focus their chat composer; settings and analytics focus their main content region.

Background

When both side panels are collapsed on desktop, the last clicked collapse button can keep focus. Pressing Enter then re-activates the rail button instead of sending the chat message. This change routes sidebar collapse through a route-owned main-region focus event rather than hard-coding every collapse to the chat input.

Implementation

• Add a typed FOCUS_MAIN_REGION custom event and a useFocusMainRegion helper.
• Dispatch the focus request after collapsing a shared sidebar collapse button.
• Register route-appropriate main focus targets for workspace chat, project creation, scratch chats, settings, and analytics.
• Avoid focusing targets inside inert/hidden regions.

Validation

• bun test src/browser/hooks/useFocusMainRegion.test.tsx src/browser/components/SidebarCollapseButton/SidebarCollapseButton.test.tsx
• bun test src/browser/components/ProjectPage/ProjectPage.autofocus.test.tsx src/browser/features/Settings/SettingsPage.test.tsx
• make typecheck
• make lint
• make static-check was attempted but the workspace is missing uvx and hadolint; other static-check subtasks that ran passed, including formatting and code-to-docs links.

Risks

Low. The new event is route-scoped by whichever main route is mounted, and sidebar expansion does not request focus. The hidden/inert guard prevents immersive overlays from returning focus to a hidden composer.

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Generated with Coder Agents on behalf of @tracyjohnsonux.

[tracyjohnsonux]

Closing because this change targeted the wrong repository. The requested fix belongs in coder/coder. Generated by Coder Agents on behalf of @tracyjohnsonux.