OIC provider adapter for Claude Code (Claude Agent SDK) #223

Context

Claude Code is the first agent runtime. Implement one provider fully before adding a second (Codex, #236). Depends on #222.

Behavior to implement

• An adapter from the Claude Agent SDK to AgentProvider: start a run with the investigation task, stream events, capture structured output, detect completion, failure, timeout, and interruption, and resume a session when possible.
• The agent uses only the tools and MCP servers configured in the runtime it runs in. A developer's local MCP setup is never assumed to exist on the remote host (OIC remote runtime: deploy on a single always-on host #233).
• Provider usage (tokens, cost) is recorded on AgentRun.usage_metadata.

Acceptance criteria

• An opt-in integration test (skipped without credentials) runs a short investigation end to end.
• Killing the agent process mid-run leaves the run failed or interrupted, never stuck in running.