[Feature]: Add Kiro CLI ACP provider support

[mfroembgen]

Before submitting

• I searched existing issues and did not find a duplicate.
• I am describing a concrete problem or use case, not just a vague idea.

Area

apps/server

Problem or use case

Kiro CLI supports ACP through kiro-cli acp, but T3 Code does not currently expose Kiro as a provider.

I also did not find Kiro in the current ACP Registry, so users cannot get it through the generic registry path today either.

Prior-art check:

• No open or closed issue matched Kiro, kiro-cli, or Kiro ACP.
• Agent Client Protocol Support #203 and Introduce an ACP adapter layer for providers #315 cover generic ACP support/adapter discussion, but not a Kiro-specific feature.
• chore: kiro cli coming soon #2228 was only a disabled Kiro placeholder and was closed as obsolete.
• [codex] Fix Kiro ACP image attachment errors #2793 contained Kiro provider work, but was closed as a cross-repo PR and redirected to a fork.
• ACP implementation bringing 31 CLI tools into t3code #2684 is an open ACP Registry PR, but Kiro is not currently included in the registry.

Proposed solution

Add a small, first-class Kiro ACP provider integration that launches:

kiro-cli acp

and maps the basic ACP session loop into T3 Code: readiness checks, session start, prompt streaming, tool/step updates, cancellation, and model selection where Kiro advertises it.

This could be implemented as a dedicated built-in provider or as an explicitly supported ACP Registry/custom ACP path if maintainers prefer that architecture.

Why this matters

Kiro users could use their Kiro subscription, custom agents, MCP setup, and CLI-native behavior inside T3 Code's existing GUI, threads, and project/worktree workflow.

Smallest useful scope

A first pass only needs to:

• detect kiro-cli
• start kiro-cli acp
• create a session
• send prompts and render streamed assistant output
• show tool calls/tool updates in the existing step UI
• support cancellation and clean shutdown
• show a helpful setup error when Kiro is missing or not authenticated

Resume, custom agents/modes, image attachments, richer permissions, and deeper model/mode UX can come later.

Alternatives considered

• Generic ACP Registry only, but Kiro is not currently in the ACP Registry.
• Reopen chore: kiro cli coming soon #2228, but that was only a placeholder.
• Reopen [codex] Fix Kiro ACP image attachment errors #2793, but a fresh issue is cleaner because that PR mixed a full provider implementation with unrelated changes and was closed as cross-repo.

Risks or tradeoffs

• Could duplicate some generic ACP Registry work if ACP implementation bringing 31 CLI tools into t3code #2684 lands first.
• Kiro-specific modes, permissions, images, and session loading need careful mapping.
• Desktop PATH/auth probing needs to work outside a normal shell environment.

Examples or references

• Kiro CLI: https://kiro.dev/docs/cli/
• Kiro ACP: https://kiro.dev/docs/cli/acp/
• Generic ACP support request: Agent Client Protocol Support #203
• Generic ACP adapter-layer request: Introduce an ACP adapter layer for providers #315
• Obsolete Kiro placeholder PR: chore: kiro cli coming soon #2228
• Closed Kiro provider PR: [codex] Fix Kiro ACP image attachment errors #2793
• Open ACP Registry PR: ACP implementation bringing 31 CLI tools into t3code #2684

Contribution

• I would be open to helping implement this.