What does this PR do?

Adds configurable Kanban worker log retention while preserving the existing default behavior.

Today worker logs rotate at a hard-coded 2 MiB and keep only one backup generation (.log.1). That is fine as a default, but long-running workers can overwrite early failure evidence before an operator has a chance to inspect it. This PR keeps the default 2 MiB + one backup, and lets operators tune retention for heavier workloads.

Related Issue

#25641

Type of Change

• 🐛 Bug fix (non-breaking change that fixes an issue)
• ✨ New feature (non-breaking change that adds functionality)
• 🔒 Security fix
• 📝 Documentation update
• ✅ Tests (adding or improving test coverage)
• ♻️ Refactor (no behavior change)
• 🎯 New skill (bundled or hub)

Changes Made

• Added kanban.worker_log_rotate_bytes to configure the per-file rotation threshold.
• Added kanban.worker_log_backup_count to configure how many rotated worker log generations are kept.
• Preserved the historical defaults:
  • worker_log_rotate_bytes: 2097152
  • worker_log_backup_count: 1
• Updated worker spawn log rotation to use the resolved config.
• Extended _rotate_worker_log() to shift multiple backup generations (.log.1, .log.2, ...).
• Added tests for default config resolution, override config resolution, and multi-generation rotation.

Reproduction

Before the fix, rotation only accepted a byte threshold and always replaced .log.1:

signature = (log_path: 'Path', max_bytes: 'int') -> 'None'
active_exists = False
backup_1 = new-run
backup_2_exists = False

After the fix, rotation accepts a backup count and preserves older generations when configured:

signature = (log_path: 'Path', max_bytes: 'int', backup_count: 'int' = 1) -> 'None'
active_exists = False
backup_1 = new-run
backup_2 = previous-run
config_override = (10, 2)

How to Test

python -m py_compile hermes_cli/kanban_db.py hermes_cli/config.py tests/hermes_cli/test_kanban_core_functionality.py

Result: passed.

/tmp/hermes-provider-refresh-venv/bin/python -m pytest -o addopts= tests/hermes_cli/test_kanban_core_functionality.py -k 'worker_log_rotation or read_worker_log_tail or gc_worker_logs'

Result: 5 passed, 151 deselected in 12.90s.
Latest local rerun: 5 passed, 151 deselected in 8.05s.

git diff --check

Result: passed.

Checklist

Code

• I've read the Contributing Guide
• My commit messages follow Conventional Commits (fix(scope):, feat(scope):, etc.)
• I searched for existing PRs to make sure this isn't a duplicate
• My PR contains only changes related to this fix/feature (no unrelated commits)
• I've run pytest tests/ -q and all tests pass
• I've added tests for my changes
• I've tested on my platform: Linux (WSL-style dev environment)

Documentation & Housekeeping

• I've updated relevant documentation (README, docs/, docstrings) — or N/A
• I've updated cli-config.yaml.example if I added/changed config keys — or N/A
• I've updated CONTRIBUTING.md or AGENTS.md if I changed architecture or workflows — or N/A
• I've considered cross-platform impact (Windows, macOS)
• I've updated tool descriptions/schemas if I changed tool behavior — or N/A

Screenshots / Logs

See reproduction and test logs above.