Add ACP Support

Feature Description

Command Code currently integrates with editors via MCP or headless mode(cmd -p --output-format json), but it cannot be embedded as an agent in editors/IDEs that speak the Agent Client Protocol (ACP). ACP is becoming the de-facto standard for editor–agent communication and is already supported by Zed, JetBrains IDEs, and Typstify, with adapters for Claude Code, Codex, OpenCode, and Cline.

Use Case

I write Typst documents in Typstify, whose v1.8.0 AI Assistant launches any ACP agent and augments it with editor-aware MCP tools: getActiveDocument, getDocumentOutline, queryDiagnostics, typstCompiler (PDF/PNG/SVG export), previewer control, and TPIX package search/download. Configuring Command Code as the agent would let me use its models, taste learning, skills, and plan mode directly inside the editor - with permission approvals in the UI and sessions I can resume - instead of switching to a terminal for every task.

Additional Context

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How important is this to you?

Blocking adoption or production use

Start by locating the existing MCP and headless integrations, then review the ACP requirements for editor-agent communication. Done should mean Command Code can be launched by ACP-compatible editors with the requested agent interaction, permission approvals, and resumable sessions.