[Feature]: Add collapsible diff

[zRelux]

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/desktop

Problem or use case

I would like to have the ability to collapse or expand files in the diff viewer, kinda like the codex app does.

Proposed solution

Ideally just a chevron at the end of the file name that collapses or expandes the diff of that file

Why this matters

It's useful when reviewing because some files generated during diffs (drizzle journal changes for example) are very big but don't need reviewing. Or used as a "reviewed tag"

Smallest useful scope

Chevron on the file name that closes the diff

Alternatives considered

No response

Risks or tradeoffs

No response

Examples or references

No response

Contribution

• I would be open to helping implement this.

[huxcrux]

I created a PR that implements this: #1125