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/__tests__/pty-attach.test.js

@@ -66,7 +66,7 @@ describe("pty-attach", () => {
       return "";
     });
     ptyAttach.attach(makeFakeWs(), "agenthub-lane-1", { cols: 80, rows: 24 });
-    assert.deepEqual(calls[0], ["set-option", "-t", "agenthub-lane-1", "mouse", "on"]);
+    assert.deepEqual(calls[0], ["set-option", "-t", "=agenthub-lane-1:", "mouse", "on"]);
   });
 
   it("still attaches even if the mouse-mode set-option call fails", () => {