[Feature]: Hide mobile sidebar after creating or selecting a thread

[chirino]

Before submitting

• I searched existing issues and did not find a duplicate.
• I am describing a concrete problem or use case, not just a vague idea.

Area

apps/web

Problem or use case

On narrow-screen layouts where the thread sidebar is collapsible/off-canvas, the sidebar currently stays open after the user creates a new thread or selects an existing one.

Proposed solution

• Clicking New thread should navigate to the thread and hide the sidebar.
• Selecting an existing thread should navigate to the thread and hide the sidebar.
• Keyboard activation of a thread row should do the same.
• Desktop/wide-screen behavior should remain unchanged.

Why this matters

• On mobile-sized layouts, leaving the sidebar open obscures the thread content the user just navigated to.
• It adds an extra manual step to close the sidebar after every thread navigation.

Smallest useful scope

• Apply this only when the sidebar is in its narrow-screen/mobile hidden state.
• Keep current desktop sidebar behavior unchanged.

Alternatives considered

No response

Risks or tradeoffs

No response

Examples or references

No response

Contribution

• I would be open to helping implement this.