Add persistent service jobs (-s flag)

Introduces a new job type for long-running systemd user services alongside
the existing timer-based jobs. Services use Type=simple with Restart=on-failure
and WantedBy=default.target — no .timer unit is created.

- New -s flag creates a service job; mutually exclusive with -t/-i/-m/-o
- Service jobs tagged with # SYSTAB_TYPE=service in their unit file
- enable/disable (-E/-D) start/stop the service in addition to toggling
  the enabled state, mirroring timer behaviour
- -S status shows ActiveState/SubState from systemd directly (avoids
  false "Inactive" for services in activating state)
- -L logs, -e edit mode, -D/-E disable/enable all handle service jobs
- Edit mode represents service jobs with 'service' as the schedule column
  (e.g. new:s,n=name | service | /path/to/cmd)
- daemon-reload runs before enable/start during service creation so
  systemd registers the new unit file first
- 22 new tests covering unit file contents, active state, disable/enable,
  named services, edit mode representation, and flag conflict errors
- New demo/services.tape and regenerated demo GIFs

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

demo/services.tape

@@ -0,0 +1,159 @@
+# systab — Persistent Services
+# Creates a managed service (no timer), checks status, disables/enables,
+# inspects via edit mode, then cleans up.
+
+Output demo/services.gif
+Set Shell bash
+Set Width 1200
+Set Height 600
+Set FontSize 16
+
+Set TypingSpeed 50ms
+
+Sleep 1s
+
+# Create a persistent service
+Hide
+Type "./demo/note.sh 'Creating a persistent service job (runs on login, auto-restarts)'"
+Enter
+Sleep 500ms
+Show
+Sleep 1s
+Type "systab -s -n monitor -c 'sleep 3600'"
+Sleep 500ms
+Enter
+Sleep 2s
+
+# Check status — should show Type: Service, Active (running)
+Hide
+Type "./demo/note.sh 'Checking status — service is running'"
+Enter
+Sleep 500ms
+Show
+Sleep 1s
+Type "systab -S monitor"
+Sleep 500ms
+Enter
+Sleep 2s
+
+# Inspect the generated unit file
+Hide
+Type "./demo/note.sh 'Inspecting the generated unit file'"
+Enter
+Sleep 500ms
+Show
+Sleep 1s
+Type "cat ~/.config/systemd/user/systab_*.service | less"
+Sleep 500ms
+Enter
+Sleep 2s
+Type "/SYSTAB_TYPE"
+Enter
+Sleep 2s
+Type "q"
+Sleep 1s
+
+# View logs
+Hide
+Type "./demo/note.sh 'Viewing service logs'"
+Enter
+Sleep 500ms
+Show
+Sleep 1s
+Type "systab -L monitor"
+Sleep 500ms
+Enter
+Sleep 2s
+
+# Disable the service
+Hide
+Type "./demo/note.sh 'Disabling the service (stops it)'"
+Enter
+Sleep 500ms
+Show
+Sleep 1s
+Type "systab -D monitor"
+Sleep 500ms
+Enter
+Sleep 2s
+
+# Verify disabled
+Hide
+Type "./demo/note.sh 'Verifying service is disabled/stopped'"
+Enter
+Sleep 500ms
+Show
+Sleep 1s
+Type "systab -S monitor"
+Sleep 500ms
+Enter
+Sleep 2s
+
+# Re-enable
+Hide
+Type "./demo/note.sh 'Re-enabling the service'"
+Enter
+Sleep 500ms
+Show
+Sleep 1s
+Type "systab -E monitor"
+Sleep 500ms
+Enter
+Sleep 2s
+
+# Open edit mode — service appears with 'service' in schedule column
+Hide
+Type "./demo/note.sh 'Service jobs appear in edit mode with schedule = service'"
+Enter
+Sleep 500ms
+Show
+Sleep 1s
+Type "EDITOR=nano systab -e"
+Sleep 500ms
+Enter
+Sleep 3s
+
+# Just view and exit
+Ctrl+X
+Sleep 2s
+
+# Also show a service created via edit mode
+Hide
+Type "./demo/note.sh 'Creating a service via edit mode: new:s | service | cmd'"
+Enter
+Sleep 500ms
+Show
+Sleep 1s
+Type "EDITOR=nano systab -e"
+Sleep 500ms
+Enter
+Sleep 3s
+
+Ctrl+V
+Sleep 500ms
+Down 5
+Sleep 500ms
+Type "new:s,n=watcher | service | sleep 7200"
+Sleep 1s
+Enter
+
+Ctrl+O
+Sleep 500ms
+Enter
+Sleep 500ms
+Ctrl+X
+Sleep 3s
+
+# Final status
+Hide
+Type "./demo/note.sh 'Both services visible in status'"
+Enter
+Sleep 500ms
+Show
+Sleep 1s
+Type "systab -S"
+Sleep 500ms
+Enter
+Sleep 3s
+
+Sleep 2s