Make long errors fully accessible

[barlevalon]

Summary

• keep status messages to one row and advertise :messages for errors
• show the complete current error in a full-screen, scrollable Messages view
• restore the originating diff or target-selector context on close
• promote PR-list failures to the shared error surface without dropping API response details
• handle keyboard and mouse scrolling, message replacement, terminal resizing, and Unicode display widths

:messages shows the current full error. Close it with q or Esc; navigation uses the existing help scrolling keys (j/k, arrows, Ctrl-d/u, g/G, Page Up/Down).

Validation

• cargo fmt --check
• cargo clippy --all-targets --all-features -- -D warnings
• cargo test — 1151 passed, 1 ignored
• cargo build
• git diff --check
• manually dogfooded at 70×16 with an oversized synthetic forge error, including full-screen rendering, selector return, and mouse/keyboard scrolling

[agavra]

I've long wanted a feature like this, thanks @barlevalon 🙏 what do you think about making it a full screen thing instead of a popup/modal? it feels a bit distracting to have it that way. Then we can eventually add things like message number/timestamps/etc.. and make it a bit more of a log (which we should probably spool it to as well, but we can do that in the future)

[barlevalon]

Thanks! I like that direction. It fits :messages better and leaves a cleaner path toward a proper message log. I’ll change the current single-message view to full-screen while keeping history, timestamps, and spooling out of scope for this PR. q/Esc will still return to the originating view.

[barlevalon]

Updated in ef0c18e: :messages now opens a full-screen Messages view rather than a popup. The originating diff/selector view is restored on q/Esc; history, timestamps, and spooling remain intentionally out of scope.

[rickgonzalez]

I chose this public PR to scan for my testing at Lenzon, I hope it's useful in some way:
https://www.lenzon.ai/viewer/cms84dh1r000dtexxsu8mhf13?voice=google-chirp3