refactor: remove dead setup_events_logger helper and unused events.log handler

[bittoby]

Summary

Removes setup_events_logger() from gittensor/utils/logging.py and its single call site in check_config(). The helper ran on every validator startup, monkey-patching logging.Logger.event onto the stdlib Logger class and opening a RotatingFileHandler on events.log, but nothing in the repository ever calls .event().

Normal bt.logging.* calls and the bittensor.log rotating file are unaffected - those flow through bittensor's LoggingMachine, not through the removed helper.

Related Issues

Closes #708

Type of Change

• Bug fix
• Refactor
• New feature
• Documentation
• Other (describe below)

Testing

• Tests added/updated
• Manually tested

Full test suite passes (410 tests). ruff check, ruff format, and pyright all clean.

Checklist

• Code follows project style guidelines
• Self-review completed
• Changes are documented (if applicable)

[bittoby]

@anderdc would you please review this PR?

[anderdc]

Cleanup is incomplete — the CLI surface for the removed feature is still registered. Please also drop the two orphan add_argument blocks in gittensor/utils/config.py:

• --neuron.events_retention_size (lines 80-85)
• --neuron.dont_save_events (lines 87-92)

Nothing consumes them after this PR, so they'd just show up in --help and silently accept values that do nothing.

[bittoby]

@anderdc Updated!