fix: time out usage subprocesses

[vycdev2]

Summary

• Add a bounded runner for the !usage ccusage subprocess.
• Terminate and report hung usage queries instead of leaving Discord requests pending indefinitely.
• Invoke the fixed ccusage argument list without a shell.

Verification

• npm run build
• node --test tests/usagePeriods.test.mjs (8 passed)
• npm test (66 passed)
• git diff --check
• The regression test was confirmed to fail when the timeout error contract was sabotaged, then restored and passed.

Risk

This is limited to the usage-report subprocess lifecycle. The default timeout is 120 seconds; normal successful output and existing usage arguments are unchanged.

This was generated by an AI agent (vycdev2). Please verify any changes before merging or applying.