fix(polymarket): force live-history backtests and remove fixture overrides

[taariq]

Summary

This PR now enforces a strict backtest data-source policy for Polymarket maker skills and replaces weak-performing/removed strategies.

Current strategy set in this PR:

• Added (replacement): polymarket/high-throughput-paired-basis-maker
• Updated: polymarket/paired-market-basis-maker
• Updated: polymarket/liquidity-paired-basis-maker
• Updated: polymarket/maker-rebate-bot
• Removed: polymarket/news-shock-guard-maker
• Removed: polymarket/resolution-decay-maker

Data Source Enforcement (No Drift)

All backtests in the maker set are now locked to the Seren Polymarket Publisher, not direct Polymarket endpoints.

Runtime policy guards

• Added SEREN_POLYMARKET_PUBLISHER_PREFIX hard checks in maker runtimes.
• Any non-Seren URL now fails fast with:
  • policy_violation: backtest data source must use Seren Polymarket publisher ...
• Backtest HTTP calls now require publisher auth header:
  • Authorization: Bearer $SEREN_API_KEY
• Missing key fails fast with:
  • missing_seren_api_key: set SEREN_API_KEY to query Seren publishers.

Config lock

• Backtest defaults now point to Seren publisher routes:
  • https://api.serendb.com/publishers/polymarket-data/markets
  • https://api.serendb.com/publishers/polymarket-data/prices-history

CI policy gate

• Added workflow: .github/workflows/enforce-seren-polymarket-publisher.yml
• CI now fails PRs if:
  • direct gamma-api.polymarket.com / clob.polymarket.com URLs appear in maker runtimes/configs
  • publisher endpoint defaults are missing
  • runtime source-policy guard or auth guard is missing

Other Reliability Fixes Retained

• live backtest sample gate (events >= min_events)
• pagination stop conditions + hard page caps
• concurrent history fetch workers
• output safety caps (total_return_pct >= -100%, max_drawdown_pct <= 100%)

Validation

• Syntax compile passed:
  • python3 -m py_compile polymarket/maker-rebate-bot/scripts/agent.py polymarket/paired-market-basis-maker/scripts/agent.py polymarket/liquidity-paired-basis-maker/scripts/agent.py polymarket/high-throughput-paired-basis-maker/scripts/agent.py
• Smoke tests passed:
  • pytest --import-mode=importlib polymarket/maker-rebate-bot/tests/test_smoke.py polymarket/paired-market-basis-maker/tests/test_smoke.py polymarket/liquidity-paired-basis-maker/tests/test_smoke.py polymarket/high-throughput-paired-basis-maker/tests/test_smoke.py
• Local policy check passed (no direct Polymarket API domains in maker runtime/config paths).