Say when a scheduled task is running

A run is detached — cron has no terminal, and the app fires it as a detached
exec — so triggering one and watching the log was indistinguishable from
triggering one that died. Worse, `claude -p` writes its answer in a single
burst at the end, so a healthy run shows nothing but its log header for as
long as it is thinking. The honest reading of the old UI was "it stalled".

triple-c-task-runner now publishes a state file per run (pid, start time, log
path) and removes it from an EXIT trap. flock remains what actually prevents
overlapping runs; this is purely observability, so every reader verifies the
pid rather than trusting the file — a container stopped mid-run cannot fire a
trap, and a task stuck on "running" forever would be a worse lie than no
indicator at all. Stale files are cleared on read.

On top of that:

- `list` grows a status column: "running 4m12s" or "idle".
- `status [--id] [--watch]` answers "is it still going?" directly, with
  elapsed time and the tail of the log when there is any output yet.
- `run` streams the log instead of blocking silently, and refuses to start a
  task that is already running.
- The Automation tab marks a running task, disables its Run now button, and
  polls while anything is in flight — including the second or two between
  firing a run and the runner registering it, which is the exact window that
  used to read as dead.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

HOW-TO-USE.md

@@ -1139,13 +1139,23 @@ triple-c-scheduler list                    # List all tasks
 triple-c-scheduler enable --id abc123      # Enable a task
 triple-c-scheduler disable --id abc123     # Disable a task
 triple-c-scheduler remove --id abc123      # Delete a task
-triple-c-scheduler run --id abc123         # Trigger a task immediately
+triple-c-scheduler run --id abc123         # Trigger a task now, streaming its log
+triple-c-scheduler status                  # What is running right now, and for how long
+triple-c-scheduler status --id abc123 -w   # Watch one task until its run finishes
 triple-c-scheduler logs --id abc123        # View logs for a task
 triple-c-scheduler logs --tail 20          # View last 20 log entries (all tasks)
 triple-c-scheduler notifications           # View completion notifications
 triple-c-scheduler notifications --clear   # Clear notifications
 ```
 
+`list` carries a status column, and the Automation tab marks a task **Running** with
+its elapsed time, so a triggered run is visible rather than silent.
+
+Note that a log which has stopped growing is not evidence of a stall: `claude -p`
+writes its answer in one go when it finishes, so a healthy run shows nothing but its
+header for as long as it is thinking. `status` is what distinguishes a slow run from
+a dead one — it reports the run only while the runner's process is genuinely alive.
+
 ### Cron Schedule Format
 
 Standard 5-field cron: `minute hour day-of-month month day-of-week`