Migrate the ClaudeAdapter from ClaudeAgentSDK.Query.run/3, which delivers
complete Message structs, to ClaudeAgentSDK.Streaming for real token-level
streaming deltas. This enables incremental output delivery through the
existing event_callback mechanism.

The event mapping is simplified: content_block_start/delta/stop events are
replaced with text_delta and tool_use_start events from the Streaming API.
Session lifecycle is now explicitly managed with start_session, send_message,
and close_session calls, with proper error handling for session failures.

The default model is changed from claude-sonnet-4-20250514 to
claude-haiku-4-5-20251001 for faster iteration during development.

Key changes:
- Switch ClaudeAdapter to ClaudeAgentSDK.Streaming for incremental deltas.
- Add process_streaming_events/2 and per-event-type handlers.
- Add tools option passthrough to ClaudeAdapter start_link/1.
- Set max_turns: 1 in SDK options for single-turn execution.
- Update oneshot example to stream content deltas to stdout.
- Bump claude_agent_sdk dependency from ~> 0.10.0 to ~> 0.11.0.
- Bump codex_sdk dependency from ~> 0.6.0 to ~> 0.7.1.
- Update all tests, mocks, fixtures, and documentation for new defaults.