What does this PR do?

Cron jobs can currently fall through to provider execution with an empty model when config.yaml has a model: section but omits model.default. That produces a lower-level provider/API error that is harder to diagnose.

This PR makes the cron path fail before starting AIAgent when no job model, HERMES_MODEL, or model.default resolves to a non-empty model. The error now points directly at the missing cron model configuration.

Related Issue

Fixes #43899

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

• cron/scheduler.py: detect the explicit model: dict-without-default case and return a clear Hermes-side error before agent startup.
• tests/cron/test_scheduler.py: add coverage that the missing default model path fails early and does not instantiate AIAgent.

How to Test

1. Configure a cron job without a job-level model.
2. Use a config.yaml with model.provider set and no model.default.
3. Run the cron job and confirm it fails with No model resolved for cron job... before the provider call.

Tested locally:

scripts/run_tests.sh tests/cron/test_scheduler.py
python3 -m py_compile cron/scheduler.py tests/cron/test_scheduler.py
git diff --check

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 (required for bug fixes, strongly encouraged for features)
• I've tested on my platform: Linux

Documentation & Housekeeping

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

Screenshots / Logs

Focused test result:

137 tests passed, 0 failed