Add plan mode support

[priyashpatil]

Adds Plan mode support to the ACP adapter, allowing users to plan first, review the proposed plan, and then either accept it for implementation or stay in planning.

Closes #182.

Credit to #195 for the foundational work this builds on.

Features Added

• Exposes Codex collaboration modes through ACP session modes and config options.
• Shows Plan mode in the same mode dropdown as the existing approval presets.
• Adds a description for Plan mode in mode/config option metadata.
• Supports request_user_input prompts through the ACP permission UI fallback.
• Shows the generated plan in an interactive Implement this plan? prompt.
• Adds plan approval actions to continue with the Default profile, continue with the Full Access profile, or reject and continue planning.
• Applies the selected approval/sandbox profile when accepting a plan for implementation.
• Marks accepted plans as User accepted plan in the tool UI.
• Marks rejected plans as Plan rejected while keeping the plan available for reference.
• Staying in Plan mode does not submit implementation.
• Keeps accepted/rejected plan text out of normal chat messages to avoid context bloat.
• Documents Plan mode in the README feature list.

[underthestars-zhy]

looks amazing!

[John0x]

@benbrandt any news on this? :)
I'd love to adapt Zed as my main agent orchestrator, but this ACP is lacking basic features, which makes it pretty much unusable for a lot of people.

[priyashpatil]

@benbrandt any news on this? :) I'd love to adapt Zed as my main agent orchestrator, but this ACP is lacking basic features, which makes it pretty much unusable for a lot of people.

I guess the review it taking some time, Just in case if you are comfortable building it locally, checkout my personal branch with more features and bug fixes: https://github.com/priyashpatil/codex-acp/tree/priyash-debug-combined

Once build locally, in agents servers in zed's settings you can do something like:

 "agent_servers": {
    "priyash-codex-acp": {
      "type": "custom",
      "command": "ABSOLUTE_PATH_TO_BUILD_BINARY",
      "args": [],
      "env": {},
    },
  }

You can ask codex to help you setup with this.

[priyashpatil]

Hey @benbrandt ,

Let me know if this PR is considerable or need some changes. I have other fixes to send which are build on top of this.

Feel free to request any changes or let me know how we should move forward.