ACP permission + mode bridge: request_permission → fork approvals; ask/accept-edits/auto-approve + model/effort config options #1711

Part of the Vibe-embedding epic (ACP-hosted vibe-acp).

Scope

Bridge ACP's host-delegated control surface into the fork's own UX and policy:

• session/request_permission: when the agent asks, surface the tool call + its options (allow_once, allow_always, reject_once, reject_always as offered) through the fork's approval flow; return the user's selection as the outcome. Timeouts/cancel must resolve as rejection, never silent approval.
• Session modes as first-class session config: ask (approval for tool executions), accept-edits (auto-approve file edits only — the agent's default), auto-approve (approve everything). Expose via session/set_mode and/or the mode config option the agent advertises in session/new.
• Model + effort config options: surface the agent's model select (tonight: mistral-medium-3.5, alias mistral-vibe-cli-latest) and reasoning-effort select (off/high observed) as settable session options, mapped to the fork's variant system.

Open verification from the spike

The 2026-11-05 spike turn ran under the default accept-edits mode and its bash call executed with zero permission requests — expected for edits, but the bash-under-accept-edits behavior needs a pinned answer: run the same turn in ask mode and prove the session/request_permission round-trip fires and is honored (deny path included: a rejected command must not execute).

Acceptance

• In ask mode, a bash tool call produces exactly one permission request; allow → executes; deny → does not execute and the agent is told.
• Switching mode/model/effort mid-session takes effect on the next turn and is reflected in the session record.