test(lanes): stop lane-lifecycle from leaking real tmux + claude processes

Four cases in lane-lifecycle.test.js call /start without stubbing PATH,
so they spawn the real system `claude` binary in a real tmux session
to simulate a stuck/live run. Each then mocks tmux's own exec calls to
fake has-session/kill-session for the app's checks, but never touches
the real spawned process — the mock only fools the app, not the OS.
Two of these leaked past every prior test run undetected (ccam-lane-22,
ccam-lane-24), surfacing in the dashboard's live "Dashboard runs" list
with no DB record and a garbage started_at, and reappearing in a
Workspace split pane pointed at a deleted temp directory.

Stub a lightweight fake `claude` on PATH (same pattern already used
correctly elsewhere in this file) instead of spawning the real CLI, and
explicitly kill the real tmux session in each test's teardown since the
app-level mock never reaches the OS process.

server/__tests__/lane-lifecycle.test.js

@@ -80,6 +80,29 @@ function makeRunChild({ exitsOnKill }) {
   return child;
 }
 
+// Puts a fake `claude` binary on PATH so a real `/start` spawns a real tmux
+// session running THIS script instead of the system Claude Code CLI. Tests
+// that mock tmux's own exec calls (to simulate a stuck/live session) still
+// spawn this real process underneath — without the stub, that spawn launches
+// the actual `claude` binary and, because the mock replaces the app's own
+// kill-session call, the real process is never actually terminated, leaking
+// a live tmux session + CLI process for good. Returns the restore function.
+function stubClaudeBinary(name) {
+  const bin = path.join(ROOT, `${name}-bin`);
+  const claude = path.join(bin, "claude");
+  fs.mkdirSync(bin, { recursive: true });
+  fs.writeFileSync(
+    claude,
+    "#!/usr/bin/env node\nprocess.on('SIGTERM', () => process.exit(0));\nsetInterval(() => {}, 1000);\n"
+  );
+  fs.chmodSync(claude, 0o755);
+  const originalPath = process.env.PATH;
+  process.env.PATH = `${bin}${path.delimiter}${originalPath}`;
+  return () => {
+    process.env.PATH = originalPath;
+  };
+}
+
 async function waitForProvisioning(id) {
   const deadline = Date.now() + 5000;
   let response;
@@ -818,6 +841,7 @@ describe("destructive lane lifecycle actions", () => {
     fs.writeFileSync(sentinel, "still here\n");
 
     // Start a run for the lane
+    const restorePath = stubClaudeBinary("await-timeout");
     const started = await request("POST", `/api/lanes/${lane.id}/start`, { prompt: "stuck" });
     assert.equal(started.status, 200);
     const runId = started.body.lane.run_id;
@@ -848,6 +872,15 @@ describe("destructive lane lifecycle actions", () => {
       assert.equal(fs.readFileSync(sentinel, "utf8"), "still here\n");
     } finally {
       tmux.__reset();
+      // The mocked kill-session above only fools the app's own check — the
+      // real tmux session + claude stub spawned above is still alive and
+      // must be killed for real, or it leaks past this test run.
+      try {
+        execFileSync("tmux", ["kill-session", "-t", runId], { stdio: "ignore" });
+      } catch {
+        // already gone
+      }
+      restorePath();
     }
     await request("DELETE", `/api/lanes/${lane.id}`);
   });
@@ -889,6 +922,7 @@ describe("destructive lane lifecycle actions", () => {
     const lane = await createManagedLane("start-twice");
 
     // Start a run for the lane
+    const restorePath = stubClaudeBinary("start-twice");
     const started = await request("POST", `/api/lanes/${lane.id}/start`, { prompt: "first" });
     assert.equal(started.status, 200);
     const runId = started.body.lane.run_id;
@@ -915,6 +949,15 @@ describe("destructive lane lifecycle actions", () => {
       assert.equal(after.body.lane.run_id, runId);
     } finally {
       tmux.__reset();
+      // The real tmux session behind the "first" run is never reset/killed
+      // in this test, mocked or otherwise — kill it for real so it doesn't
+      // leak past this test run.
+      try {
+        execFileSync("tmux", ["kill-session", "-t", runId], { stdio: "ignore" });
+      } catch {
+        // already gone
+      }
+      restorePath();
     }
 
     await request("DELETE", `/api/lanes/${lane.id}`);
@@ -1134,6 +1177,7 @@ describe("lane ensure, start mode, lane_id and releasing a finished run", () =>
     const lane = await adoptedLane("release-moved-on");
 
     // Create a run for this lane.
+    const restorePath = stubClaudeBinary("release-moved-on");
     const started = await request("POST", `/api/lanes/${lane.id}/start`, { prompt: "test" });
     assert.equal(started.status, 200, JSON.stringify(started.body));
     const runId = started.body.lane.run_id;
@@ -1161,6 +1205,14 @@ describe("lane ensure, start mode, lane_id and releasing a finished run", () =>
       assert.equal(after.status, "running");
     } finally {
       tmux.__reset();
+      // The app never calls kill-session here (healing preserves the "live"
+      // run) — kill the real tmux session directly so it doesn't leak.
+      try {
+        execFileSync("tmux", ["kill-session", "-t", runId], { stdio: "ignore" });
+      } catch {
+        // already gone
+      }
+      restorePath();
     }
   });
 
@@ -1169,6 +1221,7 @@ describe("lane ensure, start mode, lane_id and releasing a finished run", () =>
     const lane = await adoptedLane("release-stale-run");
 
     // Start a run for this lane.
+    const restorePath = stubClaudeBinary("release-stale-run");
     const started = await request("POST", `/api/lanes/${lane.id}/start`, { prompt: "test" });
     assert.equal(started.status, 200, JSON.stringify(started.body));
     const runId = started.body.lane.run_id;
@@ -1195,6 +1248,14 @@ describe("lane ensure, start mode, lane_id and releasing a finished run", () =>
       assert.equal(after.status, "idle", "status should be idle after run is gone");
     } finally {
       tmux.__reset();
+      // The app believes the session is already gone and never calls
+      // kill-session — kill the real tmux session directly so it doesn't leak.
+      try {
+        execFileSync("tmux", ["kill-session", "-t", runId], { stdio: "ignore" });
+      } catch {
+        // already gone
+      }
+      restorePath();
     }
   });
 });