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__/lanes-api.test.js

@@ -321,6 +321,27 @@ describe("/api/lanes", () => {
     await request("DELETE", `/api/lanes/${id}`);
     fs.rmSync(cwd, { recursive: true, force: true });
   });
+
+  it("router apply asks for a restart only while the lane's pane is live", async () => {
+    const tmux = require("../lib/tmux");
+    const cwd = fs.mkdtempSync(path.join(os.tmpdir(), "lane-router-live-"));
+    const id = (await request("POST", "/api/lanes", { cwd })).body.lane.id;
+    try {
+      for (const live of [false, true]) {
+        tmux.__setExecImpl((args) => {
+          if (args[0] === "has-session" && !live) throw new Error("no such session");
+          return "";
+        });
+        const r = await request("POST", `/api/lanes/${id}/router/apply`, { profile: "native" });
+        assert.equal(r.status, 200);
+        assert.equal(r.body.restart_required, live);
+        assert.equal(r.body.run_id, live ? `agenthub-lane-${id}` : null);
+      }
+    } finally {
+      tmux.__reset();
+      fs.rmSync(cwd, { recursive: true, force: true });
+    }
+  });
 });
 
 describe("hook → lane binding", () => {
@@ -396,7 +417,7 @@ describe("hook → lane binding", () => {
     assert.equal((await request("GET", `/api/lanes/${id}`)).body.lane.session_id, "sess-b");
     assert.equal((await request("GET", `/api/lanes/${id}`)).body.lane.needs_action, "blocked");
 
-    // Session B's second PostToolUse clears the flag (B is now bound)
+    // B is bound now, but it still did not raise the flag: A is still waiting.
     await request("POST", "/api/hooks/event", {
       hook_type: "PostToolUse",
       data: {
@@ -406,6 +427,18 @@ describe("hook → lane binding", () => {
         tool_use_id: "t2",
       },
     });
+    assert.equal((await request("GET", `/api/lanes/${id}`)).body.lane.needs_action, "blocked");
+
+    // A answering its own prompt is what clears it.
+    await request("POST", "/api/hooks/event", {
+      hook_type: "PostToolUse",
+      data: {
+        session_id: "sess-a",
+        cwd: "/tmp/lane-cross-session",
+        tool_name: "Read",
+        tool_use_id: "t3",
+      },
+    });
     assert.equal((await request("GET", `/api/lanes/${id}`)).body.lane.needs_action, null);
 
     await request("DELETE", `/api/lanes/${id}`);