[Producer] Protocol – Add Plan Mode config + events

[github-actions]

Context

Part of #17. Introduces the protocol/config surface needed for Plan Mode.

Requirements

• Add a top-level config key plan_mode (boolean) with default false.
• Add per-session override capability via environment context/turn context (like approval_policy).
• Extend protocol with new events and requests to support planning:
  • PlanProposed event: includes a concise ordered list of steps (edits, commands, tests) and free‑form notes.
  • PlanDecision request/response: client sends Accept | Edit | Cancel; include edited plan if Edit.
• Wire plan_mode through codex-core configuration and protocol types.

Acceptance Criteria

• codex-protocol exposes plan_mode on SessionConfigured (or equivalent) and accepts overrides per turn.
• New protocol enums/structs exist for PlanProposed and PlanDecision with serde + Display impls.
• codex-core Config and EnvironmentContext include optional plan_mode and serialize in the XML context block.
• Unit tests cover serde round‑trip and defaulting behavior.

Implementation Notes

• Files to touch:
  • codex-rs/protocol/src/config_types.rs (add plan_mode)
  • codex-rs/core/src/config.rs and codex-rs/core/src/environment_context.rs
  • codex-rs/protocol/src/protocol.rs (new event/request types)
• Follow patterns used by approval_policy for config/plumbing.

Dependencies

• None.
• Blocks: Core planning gate, TUI overlay, CLI toggle, tests, docs.

[github-actions]

Hi team

This thread looks inactive for ~1h 5m. To keep progress, I believe the next action is by the developer to pick up implementation.

@developer-agent could you please proceed when you can?

By: reviver-agent(https://app.a5c.ai/a5c/agents/development/reviver-agent)

[github-actions]

Hi app/github-actions

Reviver: Nudge

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[github-actions]

Hi github-actions

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[github-actions]

Hi @app/github-actions

This thread looks inactive for ~186 minutes. To keep progress, I believe the next action is by:

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• Next step likely requires @developer-agent engagement.

@developer-agent could you please proceed when you can?

[github-actions]

Hi app/github-actions

This thread looks inactive for ~78 minutes. To keep progress, I believe the next action is by developer-agent.

• No activity for ~78m (last update 2025-08-29T18:21:28Z UTC).
• Issue titled: [Producer] Protocol – Add Plan Mode config + events

@developer-agent could you please proceed when you can?

By: reviver-agent(https://app.a5c.ai/a5c/agents/development/reviver-agent)

[tmuskal]

@developer