feat(cron): per-job workdir for project-aware cron runs (#15110)

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 dir 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 (no project context files, tools
use the scheduler's cwd).

Requested by @bluthcy.

## Mechanism

- 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 to 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.

## 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.
- Full targeted suite (tests/cron/, test_cronjob_tools.py, test_cron.py,
  test_config_cwd_bridge.py, test_worktree.py): 314/314 passed.
- Live smoke: hermes cron create --workdir $(pwd) works; relative path
  rejected; list shows 'Workdir:'; edit --workdir '' clears.

hermes_cli/cron.py

@@ -93,6 +93,9 @@ def cron_list(show_all: bool = False):
         script = job.get("script")
         if script:
             print(f"    Script:    {script}")
+        workdir = job.get("workdir")
+        if workdir:
+            print(f"    Workdir:   {workdir}")
 
         # Execution history
         last_status = job.get("last_status")
@@ -168,6 +171,7 @@ def cron_create(args):
         skill=getattr(args, "skill", None),
         skills=_normalize_skills(getattr(args, "skill", None), getattr(args, "skills", None)),
         script=getattr(args, "script", None),
+        workdir=getattr(args, "workdir", None),
     )
     if not result.get("success"):
         print(color(f"Failed to create job: {result.get('error', 'unknown error')}", Colors.RED))
@@ -180,6 +184,8 @@ def cron_create(args):
     job_data = result.get("job", {})
     if job_data.get("script"):
         print(f"  Script: {job_data['script']}")
+    if job_data.get("workdir"):
+        print(f"  Workdir: {job_data['workdir']}")
     print(f"  Next run: {result['next_run_at']}")
     return 0
 
@@ -218,6 +224,7 @@ def cron_edit(args):
         repeat=getattr(args, "repeat", None),
         skills=final_skills,
         script=getattr(args, "script", None),
+        workdir=getattr(args, "workdir", None),
     )
     if not result.get("success"):
         print(color(f"Failed to update job: {result.get('error', 'unknown error')}", Colors.RED))
@@ -233,6 +240,8 @@ def cron_edit(args):
         print("  Skills: none")
     if updated.get("script"):
         print(f"  Script: {updated['script']}")
+    if updated.get("workdir"):
+        print(f"  Workdir: {updated['workdir']}")
     return 0