Legacy OMP chat retirement criteria, dead-code removal, upstream submission #77

Summary

Record when the legacy OMP chat path may be retired, delete only code made unreachable by the cutover, and submit the Orca work upstream as focused stablyai/orca PRs.

Context

• 44madfire/orca#20: legacy stays until explicitly retired; final implementation suitable for focused upstream contribution; no removal of ordinary terminal OMP.
• Legacy remains the routed path for WSL, runtime-owned SSH targets, Windows without start-time proof, terminal-launched and mobile-launched OMP, and stale mobile builds (plan §3.10–3.12; decision D7).

Scope

• Decision record for D7 on Tracking: OMP Native Chat → ACP migration (v3 plan) #67. No legacy route is retired before adoption (Post-cutover migration: adopt existing legacy OMP sessions into ACP chat #69) and handoff (Post-cutover migration: persisted ACP↔Terminal handoff for OMP chats #84) exist for the sessions it serves.
• Delete only code with no remaining route (verify each symbol); keep everything ordinary terminal OMP and remaining fallbacks use.
• Upstream PR set: provider-neutral units (Structured launch availability per registered agent, with legacy-chat fallback on decline #78, Resting model catalog for registered structured agents from their model probe spec #79, generic part of Post-cutover migration: adopt existing legacy OMP sessions into ACP chat #69, ACP compaction updates → compaction boundary and usage invalidation (provider-neutral) #80, ACP elicitation forms and OMP approval-policy parity #81, Mobile: render and drive registered structured agents (provider-neutral) #72, Single-writer protection for ACP-held OMP sessions (resume guards, AI Vault ownership) #83, generic runtime/dialect hooks of Register omp acp as an opt-in structured ACP agent behind the availability gate #68 and OMP dialect: mid-turn "Send now" steers via OMP's ACP steer extension #82) and OMP units (Register omp acp as an opt-in structured ACP agent behind the availability gate #68, OMP live timeline parity: messages, reasoning, tools, edits, errors, usage #70, OMP commands, options and composer over ACP #71, OMP dialect of OMP dialect: mid-turn "Send now" steers via OMP's ACP steer extension #82, OMP ACP lifecycle: settlement, Stop, crash, restart, status, notifications #73, New OMP chats default to ACP when the provider satisfies orca-native-chat-v1 #74, Post-cutover migration: persisted ACP↔Terminal handoff for OMP chats #84), each with the PR template filled.

Non-goals

• No removal of a supported legacy route without the D7 decision; no provider changes.

Depends on

• Post-cutover migration: persisted ACP↔Terminal handoff for OMP chats #84

Parity rows owned

• None.

Acceptance criteria

• D7 recorded with the list of remaining legacy routes.
• Removed code has no remaining caller (typecheck + tests green).
• Upstream PRs opened, each focused and independently reviewable.
• No omp --mode rpc path exists.

Required tests

• Routing matrix from Structured launch availability per registered agent, with legacy-chat fallback on decline #78 still green after removals; terminal OMP snapshot tests unchanged.

Base branch

acp-migration (44madfire/orca).