feat(cron): per-job workdir for project-aware cron runs

[teknium1]

Cron jobs can now specify a per-job working directory. When set, the job runs as if launched from that directory — AGENTS.md / CLAUDE.md / .cursorrules from that directory are injected into the system prompt, and the terminal / file / code-exec tools use it as their cwd (via TERMINAL_CWD). When unset, old behaviour is preserved.

Requested by @bluthcy on X.

Changes

• cron/jobs.py: create_job / update_job accept workdir, validated to be an absolute existing directory at create/update time.
• cron/scheduler.py run_job: if job.workdir is set, point TERMINAL_CWD at it and flip skip_context_files=False before building the agent. Restored in finally on every exit path.
• cron/scheduler.py tick: workdir jobs run sequentially (outside the thread pool) because TERMINAL_CWD is process-global. Workdir-less jobs still run in the parallel pool unchanged.
• tools/cronjob_tools.py + hermes_cli/cron.py + hermes_cli/main.py: expose workdir via the cronjob tool and hermes cron create/edit --workdir .... Empty string on edit clears the field.
• Docs: website/docs/user-guide/features/cron.md — new section with examples and the serialization note.

Usage

# CLI
hermes cron create --workdir /home/me/projects/acme \
  --schedule 'every 1d at 09:00' \
  --prompt 'Audit open PRs, summarize CI, post to #eng'

# From chat — via the cronjob tool
cronjob(action='create', schedule='every 1d at 09:00',
        workdir='/home/me/projects/acme',
        prompt='...')

Validation

• tests/cron/test_cron_workdir.py (21 tests): normalize, create, update, JSON round-trip via cronjob tool, tick partition (workdir jobs run on the main thread, not the pool), run_job env toggle + restore in finally.
• Targeted sweep (cron + cronjob tool + cli cron + config-cwd-bridge + worktree): 314/314 passed.
• Live smoke: hermes cron create --workdir \$(pwd) works; relative path rejected with a clear error; cron list shows Workdir:; cron edit --workdir '' clears.

Design notes

• Workdir is process-global via TERMINAL_CWD — that's why tick partitions workdir jobs off the parallel pool. Alternative was plumbing a cwd param through AIAgent + 8 tool files (~150 LOC vs 60); rejected as out of scope for the feature's actual usage pattern (users have 1-3 workdir jobs, not 20).
• Default workdir=None is unchanged: no AGENTS.md injection, no env mutation, same parallel tick behaviour. Zero impact on existing users.