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>

app/src/lib/types.ts

@@ -388,6 +388,10 @@ export interface ScheduledTask {
   last_run: string | null;
   /** Known only for enabled one-shot tasks; cron is not evaluated. */
   next_run: string | null;
+  /** A run is in flight right now (the runner's pid was verified live). */
+  running: boolean;
+  /** When that run started. Null unless `running`. */
+  running_since: string | null;
 }
 
 /** Mirrors Rust `ScheduleKind` — which of the scheduler's two `add` flags to