Add /compact

[easong-openai]

Adds an initial /compact command that summarizes the existing conversation and also introduces scrolling to the slash command modal. There's probably more work to do on the prompt.

[github-actions]

Summary

Makes several codex-rs core modules public and overhauls the TUI: adds scroll-aware slash-command popup, new widgets/event types, related tests, and minor model/client tweaks.

Review

Nice functional upgrade and tidy Rust implementation! A few quick suggestions:

• Exporting client, client_common, models, and ResponseStream widens the public API — consider a re-export module or #[doc(hidden)] guards to avoid an unnecessary semver bump.
• visible_rows: Cell<usize> is mutated only in render; a plain usize returned from the calc would avoid interior mutability.
• Please run just fmt / cargo fmt to fix a handful of rustfmt nits (long lines in command_popup.rs).
• Add a short note to CHANGELOG and TUI help about the new scrolling behaviour.

Other than those minor points, looks solid and the added tests are great.

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[nornagon-openai]

won't this result in repeatedly appending to the base instructions if using /compact more than once?

[bolinfest]

Adding @pakrym-oai and @ibahmed-oai as reviewers because there was already a lot of discussion on a related PR: #1529

[aibrahim-oai]

I talked about this with @easong-openai . This approach is building on top of #1495 and #1497 . We thought that this approach isn't the best because we are calling the model in tui. Also, this will make it harder to use /compact in the mcp because we will have to build the same thing again.

As @bolinfest mentioned, we had good iterations on #1527 and #1529 . I think this is a better appraoch because the logic goes to the /core. Admittedly, the approach makes the summary appear in the tui which may not be the best UX but I think you can go around that in the tui implementation.