fix(cli-agent): keep Kiro multiline input visible

Description

Problem

Warp's first-class Kiro integration enables the coding-agent footer for Kiro sessions. Kiro V3 renders a live prompt that grows toward the bottom of the terminal; on Warp v0.2026.10.14.08.27.stable_01 for macOS, repeated Shift+Enter input descends behind the footer and hides the cursor line.

Kiro already decodes the relevant terminal encodings, including Ctrl+J, CSI-u Shift+Enter, xterm modifyOtherKeys, and ESC-prefixed Enter. The incompatible behavior begins at Warp's footer insertion boundary.

What changes

• Treat Kiro as not supporting Warp's CLI-agent footer.
• Keep Kiro command detection, branding, session tracking, and telemetry unchanged.
• Add a regression test that verifies a Kiro session neither enters footer render state nor receives a footer rich-content block.
• Extend the CLI-agent property test so Claude remains footer-capable while Kiro opts out.

This is intentionally narrow: no terminal detection, input rewriting, global footer switch, or behavior change for other CLI agents.

Decision and tradeoff

The fix restores the viewport ownership Kiro had before Warp added first-class Kiro footer support. Kiro sessions temporarily lose Warp's coding-agent toolbar, but their self-rendered prompt retains all terminal rows and can scroll correctly.

The alternative of changing Kiro's input height or decoder was rejected because the exact reported Kiro nightly and current Kiro tests already handle all relevant key sequences. Disabling the footer broadly was rejected because other supported agents use bounded composers and retain compatible footer behavior.

Linked Issue

Follow-up to #9066 and #16243.

• 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

• Red-before / green-after regression:
  • cargo test -p warp cli_agent_footer_does_not_render_for_kiro_session -- --nocapture
  • Failed against the previous footer capability, then passed with this change.
• cargo test -p warp test_warp_tui_variant_properties -- --nocapture
• cargo clippy -p warp --lib --tests -- -D warnings
• ./script/format
• cargo build -p warp --bin warp-oss
• E2E: locally built Warp OSS, Linux/X11 at 1440×900, exact Kiro CLI 2.33.1-nightly.3, real Shift+Return key events.
  • Replayed the reported sequence: hello, 4 newlines, new line, 4 newlines, asdfasdf, 4 newlines, asdfsaf.
  • Added 24 more Shift+Enter events; deep-marker-visible remained visible.
• Release comparison on Linux:
  • v0.2026.09.30.08.29.stable_03: before first-class Kiro support; no footer.
  • v0.2026.10.07.08.29.stable_03: first release with Kiro integration/footer.
  • v0.2026.10.21.08.25.stable_02: footer still present.

The repository has no pr-check:quick command, so the targeted tests, Clippy, formatter, and OSS build above were used.

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

The fix was manually tested using the locally built warp-oss binary instead.

Screenshots / Videos

• Public E2E evidence report
• 16-second E2E recording
• Representative multiline frame

Limitation: the original macOS failure was directly verified from the reporter's recording. The after-fix build was exercised on Linux/X11 because a macOS test host was unavailable. Released Linux builds did not reproduce the overlap, so the macOS-specific rendering surface is inferred from the direct recording, release boundary, and source behavior.

Agent Mode

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

CHANGELOG-BUG-FIX: Fixed Kiro CLI multiline prompts being hidden behind Warp's coding-agent toolbar.