fix(tmux,run,hooks): the four pre-existing bugs the #37 evaluation found

- tmux targets are exact (`=name`, `=name:` for panes/options): a bare
  `-t agenthub-lane-1` resolves by prefix to agenthub-lane-12 once lane 1
  is gone, so killing a finished lane could kill another.
- getRun/killRun refuse ids that are not `agenthub-lane-<n>`, so
  DELETE /api/run/main can no longer kill a user's own tmux session.
- router/apply reports restart_required only for a running pane; getRun
  returns a `gone` handle, so it was always true.
- needs_action is cleared only by the session that raised it (new nullable
  lanes.needs_action_session); a second session in the same cwd used to
  clear it on its second hook.

server/routes/lanes.js

@@ -690,7 +690,7 @@ router.post("/:id/router/apply", sameOriginGuard, (req, res) => {
     // outside; the pane has to be restarted. Report it instead of letting the
     // switch look clean and then fail on the user's next prompt.
     const runId = runs.runIdForLane(lane.id);
-    const live = !!runs.getRun(runId);
+    const live = runs.getRun(runId)?.status === "running";
     // Every other mutating lane route broadcasts; without it the client's
     // cached row keeps the OLD router_profile, and the next lane switch
     // re-reads that stale row and flips the picker back.