[Feature]: Add per-project default right panel tabs for new threads

[OffCrazyFreak]

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

Right panel state is persisted per thread, but every new thread starts with an empty, closed panel. Users who routinely work with Files and Diff must reopen and configure the panel for every thread.

Proposed solution

Add an off-by-default, user-specific setting per project that initializes new threads with selected right panel surfaces. A useful initial preset would open Diff and Files, with Files active while the thread is still a draft. Initialize the state only during new-thread creation so manually closing the panel remains respected.

Why this matters

It removes repetitive panel setup while preserving the current default experience for everyone else.

Smallest useful scope

A per-project “Open Diff and Files for new threads” switch stored in client settings.

Alternatives considered

No response

Risks or tradeoffs

Preferences should use scoped project keys for multiple environments. Diff may not be available until a draft becomes a server thread. Deleted-project preference entries may need eventual cleanup.

Examples or references

No response

Contribution

• I would be open to helping implement this.