feat: Phase A ACP Bridge Foundation

[falfaddaghi]

Summary

Implements the remaining Phase A ACP bridge foundation work needed for side-kick-ready tool and permission flows. The bridge now forwards ACP tool-call activity as OpenCode-compatible SSE events, supports configurable permission handling, and preserves Nexus session/message context for emitted events while keeping existing auto-approval behavior as the default.

Plan: docs/tasks/phase-a-acp-bridge-foundation-e1d223a4/plan-phase-a-acp-bridge-foundation-e1d223a4.md

ADW tracking ID: e1d223a4

Checklist

• Added shared bridge and browser OpenCode event types for tool-call and permission events
• Added permission mode and timeout configuration via CLI/env/default parsing
• Translated ACP tool_call and tool_call_update notifications into SSE events with session, message, and call identifiers
• Implemented forwarded permission request lifecycle with pending request resolution and timeout handling
• Added POST /session/:id/permission handling and per-session permission mode support in the bridge server
• Updated OpenCode permission service typings/helpers for bridge permission responses
• Documented bridge permission configuration in env examples and bridge README
• Added/updated bridge tests for config, adapter permission/tool events, and server route behavior

Key Changes

• Extended packages/nexus-acp-bridge types, adapter, server, and config plumbing for auto and forward permission modes.
• Added OpenCode-compatible tool.call, tool.call.updated, and permission.requested events across bridge and frontend type definitions.
• Added bridge integration coverage around permission forwarding, response resolution, event delivery, and configuration parsing.
• Preserved compatibility for existing workflow and prompt generation consumers that ignore the new event variants.