consolidate 19 GTM bots into researcher/strategist/executor; remove playwright from botticelli

- Delete 19 standalone bot dirs: market_signal, customer_discovery, pain_alternatives,
  segment_qualification, pipeline_qualification, experiment_design, mvp_validation,
  positioning_offer, pricing_validation, gtm_economics_rtm, admonster,
  creative_paid_channels, pilot_delivery, partner_ecosystem, retention_intelligence,
  churn_learning, owl, owl_strategist, marketing_strategist
- Move all *_tools.py files into researcher/, strategist/, executor/
- Move experiment_execution.py and setup_schema.json into executor/
- Inline all setup_handlers directly in researcher/strategist/executor main loops
- Remove scan_brand_visuals tool and playwright from botticelli; replace with web tool
- Add setup_handlers to owl3_bot and productman_bot for reuse by consolidated bots
- Add BOT_BEST_PRACTICES.md with architectural guidelines

Author: lev-goryachev