Fix CI test (3.10) failure by resolving Ruff lint violations

[Copilot]

test (3.10) was failing in GitHub Actions at the lint stage (ruff check aether/). The failure was caused by a set of F401/F841/F541 violations introduced across CLI, threat modeling, webhook, and tool modules.

• Lint breakage resolved (root-cause changes)

  • aether/cli.py
    • Removed unused logging import.
    • Ensured setup_logging() is actually invoked from main() so the import is no longer dead.
  • aether/threat_modeling.py
    • Removed unused local variable assignment.
    • Replaced placeholder-less f-string with a plain string literal.
  • aether/tools/executor.py
    • Removed unused Tool import; retained only ToolResult.
  • aether/tools/memory_query.py
    • Removed unused typing.Optional import.
  • aether/webhooks/github_webhook.py
    • Removed unused local assignment from run_react_loop(...).
    • Replaced placeholder-less f-string with a plain string.

• Representative change

  # before
  state = aether.run_react_loop(goal=goal, max_steps=8)
  logger.info(f"Remediation completed successfully.")
  
  # after
  aether.run_react_loop(goal=goal, max_steps=8)
  logger.info("Remediation completed successfully.")