fix: Reranker now uses real LLM via next() — no more BM25 fallback

- Reranker saves/clears _thinking_blocks around its model call to
  prevent interference with the main agent loop's thinking round-trip
- AnthropicModelAdapter.next() now correctly routes through the Reranker
- disableThinking flag prevents extended thinking for non-Anthropic
  endpoints where our message format can't preserve thinking blocks

Verified: multi-step tool calls + Reranker work together without
API errors. The LLM Reranker now actually curates memories.

737 passed, 2 skipped

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Author: QUSETIONS