feat: add debuggable deep search tracing

[BBear0115]

Summary

• Adds a debuggable deepsearch tool that runs a bounded Search - Read - Search loop with maxdepth protection.
• • Adds structured JSONL tracing for search crawl read cache-hit provider payload output preview errors and exploration-tree metadata.
• • Adds opt-in local JSON caching for search/crawl results via OPENCMODEEPSEARCHCACHE=1.
• • Adds opt-in CLI breakpoints for deep search via OPENCMODEEPSEARCHBREAKPOINTS=1 guarded by TTY detection so web/API deployments do not block.
• • Wires deepsearch into the CMO Agent and Blog SEO Expert.
    Closes [Feature] 🚀 Introduce "Debuggable Deep Search" Strategy — Make the AI CMO's Reasoning Transparent! #1

Verification

• env PYTHONPATH=src python -m pytest tests/testdeepsearchtrace.py tests/testdeepsearch.py tests/testcrawl.py tests/testsmoke.py - 25 passed
• • env PYTHONPATH=src python -m pytest - 670 passed 3 skipped

Notes

• Tracing is enabled by default and can be disabled with OPENCMODEEPSEARCHTRACE=0.
• • Cache reuse is opt-in to avoid stale research results in production.