ACP elicitation forms and OMP approval-policy parity #81

Summary

Support ACP elicitation/create forms as Orca question/approval items (provider-neutral) and make OMP approval prompts follow the user's OMP policy, so questions, approvals and plan proposals behave as in legacy chat.

Context

• 44madfire/orca#20: questions/approvals/interactions parity; exactly-once interaction responses.
• Orca's initialize advertises only fs and terminal (src/main/acp/acp-session-runtime.ts:107 @76d1b7b) and handles no elicitation/create.
• Without elicitation.form OMP strips the ask tool (interactivePrompts gate, packages/coding-agent/src/modes/acp/acp-agent.ts:1227 @53f253f), resolves extension select/confirm/input as empty, and auto-approves plan proposals (:2020).
• OMP's ACP gate requests permission for every bash/edit/delete/move unless an explicit yolo opt-in is set, while the TUI default policy is yolo (packages/coding-agent/src/session/session-tools.ts:911-928, packages/coding-agent/src/session/acp-permission-gate.ts:7-12 @53f253f).
• Orca answers permissions after a journal compare-and-set and auto-allows under full access (src/main/acp/acp-structured-acquire.ts:133-149 @76d1b7b).

Scope

• Generic, standard ACP: advertise elicitation.form in clientCapabilities (probed normally; no OMP marker); map select, confirm, text input and multi-question forms onto existing question/approval journal items with commit-before-reply; decline on Stop/steer/close; decline unsupported schemas (never hang).
• OMP: opt in; plan proposals shown as a decision.
• Approval policy: when the provider confirms orca-native-chat-v1 (Register omp acp as an opt-in structured ACP agent behind the availability gate #68 negotiation), OMP decides when to ask exactly as the TUI does (ACP permission gate follows the configured approval policy for orca-native-chat-v1 clients oh-my-pi#14); Orca full access maps to OMP's explicit auto-approve launch flag rather than answering allow_once.
• Status is blocked while any request is pending.

Non-goals

• No renderer plugin surface; no URL elicitation; no Grok behavior change.

Depends on

• Register omp acp as an opt-in structured ACP agent behind the availability gate #68
• ACP permission gate follows the configured approval policy for orca-native-chat-v1 clients oh-my-pi#14

Parity rows owned

• P-APPR-01, P-APPR-02, P-APPR-03, P-INTR-01, P-PLAN-02.

Acceptance criteria

• Model ask questions render as question cards and the answer reaches OMP once.
• Default-config OMP prompts for approval exactly when the TUI would; full access never prompts.
• Plan proposals wait for the user's decision.
• Stop with an open question/approval declines it once and ends the turn.
• Status is blocked while waiting, on desktop and mobile.

Required tests

• Round-trip for each form kind.
• Desktop and mobile answering the same request → one reply, one refusal.
• Answer after Stop → refused; malformed schema → declined.
• Permission request and elicitation concurrently; reattach with a pending request → withdrawn.

Base branch

acp-migration (44madfire/orca).