feat: OpenCode project settings #348

Why

OpenCode returns in beta.2 on project config (master plan Decision 2).

In scope

mcp, instructions, plugins and skills in .opencode/; approvals scoped to the project; remove the user OpenCode lifecycle.

Out of scope

User opencode.json.

Acceptance criteria

• Nothing under ~/.config/opencode changes
• OpenCode in the project sees the MCP servers and guidance

Dependencies

Blocked by: #340

Blocks: #349, #386

Plan

• Release: 4.0.0-beta.2
• Size: size:M · Workstream: ws:project-scope
• Epic: feat: project-scope P3, Codex and OpenCode project settings (epic) #298
• Card: P3-05 in the card inventory
• Sources: Design (docs(plans): project-scoped management design and its prerequisites #289) Hosts; Supersession ledger (docs(plans): v4 GA master plan, supersession ledger and v5 registers #290) ADR-0017

Verification

• Contract test from test: contract tests with the current violations as baseline #328