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__/tmux.test.js

@@ -51,7 +51,7 @@ describe("tmux wrapper", () => {
       "--model",
       "opus",
     ]);
-    assert.deepEqual(calls[1], ["set-option", "-t", "agenthub-lane-1", "mouse", "on"]);
+    assert.deepEqual(calls[1], ["set-option", "-t", "=agenthub-lane-1:", "mouse", "on"]);
   });
 
   it("sendText types the literal string and presses Enter, with no quoting", () => {
@@ -64,11 +64,25 @@ describe("tmux wrapper", () => {
     assert.deepEqual(calls[0], [
       "send-keys",
       "-t",
-      "agenthub-lane-1",
+      "=agenthub-lane-1:",
       "-l",
       'Reminder: run "agenthub stage implement"',
     ]);
-    assert.deepEqual(calls[1], ["send-keys", "-t", "agenthub-lane-1", "Enter"]);
+    assert.deepEqual(calls[1], ["send-keys", "-t", "=agenthub-lane-1:", "Enter"]);
+  });
+
+  it("targets a session exactly, so lane 1 never resolves to lane 12 by prefix", () => {
+    const calls = [];
+    tmux.__setExecImpl((args) => {
+      calls.push(args);
+      return "";
+    });
+    tmux.hasSession("agenthub-lane-1");
+    tmux.killSession("agenthub-lane-1");
+    assert.deepEqual(calls, [
+      ["has-session", "-t", "=agenthub-lane-1"],
+      ["kill-session", "-t", "=agenthub-lane-1"],
+    ]);
   });
 
   it("killSession never throws when the session is already gone", () => {