warpui_tui: TuiPresenter + first-class TuiBackend::Presenter

[zachbai]

Description

Linked Issue

• The linked issue is labeled ready-to-spec or ready-to-implement.
• Where appropriate, screenshots or a short video of the implementation are included below (especially for user-visible or UI changes).

Testing

• I have manually tested my changes locally with ./script/run

Screenshots / Videos

Agent Mode

• Warp Agent Mode - This PR was created via Warp's AI Agent Mode

[zachbai]

Warning

This pull request is not mergeable via GitHub because a downstack PR is open. Once all requirements are satisfied, merge this PR as a stack on Graphite.
Learn more

• warpui_tui: crossterm renderer + runtime; wire runtime to TuiPresenter #12417
• warpui_tui: TuiPresenter + first-class TuiBackend::Presenter #12416 👈 (View in Graphite)
• warpui_tui: TUI elements (text, column, container, child-view, event-handler) #12415
• warpui_tui: crate foundation - geometry, buffer, TuiElement, events #12414
• warpui_core: backend-neutral core with an additive tui feature #12413 : 1 other dependent PR (#12633 )
• master

This stack of pull requests is managed by Graphite. Learn more about stacking.

[zachbai]

Superseded: the warpui_tui crate was absorbed into warpui_core behind a purely additive tui feature. The content of this PR (ported and adapted to the unified View API with a typed render path) now lands via #12601, on the consolidated foundation #12413.