docs(readme): restore beta documentation entrypoints

Restores the three required exact strings that the static test
test_beta_docs_index_static::test_entrypoints_link_beta_index
asserts must be present in README.md:

  - "Beta Docs Index"
  - "Beta Rollout Operator Command Center"
  - "Beta Rollout Operator Master Checklist"

Adds minimal "Beta Documentation" section with links and a
one-line safety note. No other content changed.

Local test run: 68 passed (60 safety + 8 beta docs).
validate_safety_config.py: OVERALL PASS.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: Melly-999

README.md

@@ -262,6 +262,18 @@ config.json       Runtime safety config (autotrade=false, dry_run=true)
 
 ---
 
+## Beta Documentation
+
+For source-only beta operations, start here:
+
+- [Beta Docs Index](docs/beta/README.md)
+- [Beta Rollout Operator Command Center](docs/beta/beta_rollout_operator_command_center.md)
+- [Beta Rollout Operator Master Checklist](docs/qa/beta_rollout_operator_master_checklist.md)
+
+> Source-only beta is read-only, dry-run-only, and manual. It does not approve live trading, broker execution, investment advice, or generated artifact releases.
+
+---
+
 ## Disclaimer
 
 This repository is for **educational, research, and paper-trading portfolio demonstration purposes only**.