feat(opencode): diffs total

[aarvinr]

Issue for this PR

Closes #14231

Type of change

• Bug fix
• New feature
• Refactor / code improvement
• Documentation

What does this PR do?

A total diffs counter in the sidebar¹ next to the "Modified Files" header, showing the total number of lines of code added and deleted in a session. Previously, only individual diff counters for each modified file were shown.

This is helpful for assessing the total work of an agent and fits naturally into the interface.

How did you verify your code works?

Typecheck + verifying behavior locally. (See screenshot below for example.)

Screenshots / recordings

Checklist

• I have tested my changes locally
• I have not included unrelated changes in this PR

If you do not follow this template your PR will be automatically rejected.

Footnotes

1. https://github.com/anomalyco/opencode/blob/dev/packages/opencode/src/cli/cmd/tui/routes/session/sidebar.tsx ↩

[github-actions]

Hey! Your PR title [FEATURE]: Total diffs counter in sidebar doesn't follow conventional commit format.

Please update it to start with one of:

• feat: or feat(scope): new feature
• fix: or fix(scope): bug fix
• docs: or docs(scope): documentation changes
• chore: or chore(scope): maintenance tasks
• refactor: or refactor(scope): code refactoring
• test: or test(scope): adding or updating tests

Where scope is the package name (e.g., app, desktop, opencode).

See CONTRIBUTING.md for details.

[colinandres885-boop]

https://holafelix.com/request/ac51a1ca-5b7d-4a21-b779-c5691729ddf4

[aarvinr]

https://holafelix.com/request/ac51a1ca-5b7d-4a21-b779-c5691729ddf4

Spam/scam?