keep idle workers alive: bump_idle_ttl + KeepAlive heartbeat

Root cause: idalib workers run an idle watchdog (worker_lifecycle.py) that
self-exits after idle_ttl_sec (default 600s) of no requests -- deliberate
resource hygiene for a shared/ephemeral supervisor, wrong for an interactive
TUI. CLI-opened startup binary always gets 600s (no flag).

Fix (both verified against a 12s-TTL session):
- IDAClient.bump_idle_ttl(1e9): re-open (idempotent) re-applies TTL, no upper
  cap -> effectively immortal. Primary fix, call once at startup.
- IDAClient.keepalive()/KeepAlive: background server_health heartbeat resets the
  watchdog; covers adopted sessions too. Safety net.

tests/test_keepalive.py: 4/4 (heartbeat + bump both keep a short-TTL worker
alive past 2x TTL). docs updated with why + fix.

1 files changed, 76 insertions, 0 deletions

diff --git a/tests/test_keepalive.py b/tests/test_keepalive.py
new file mode 100644
index 0000000..2910e1a
--- /dev/null
+++ b/tests/test_keepalive.py
@@ -0,0 +1,76 @@
+#!/usr/bin/env python3
+"""Prove that an interactive session can 'just chill' without the worker idling
+out. Uses a deliberately short worker TTL to keep the test fast.
+
+    python3 tests/test_keepalive.py
+
+Needs ~/ida-venv + a running server (tests/serverctl.sh) and a writable target.
+"""
+import os
+import sys
+import time
+
+HERE = os.path.dirname(os.path.abspath(__file__))
+REPO = os.path.dirname(HERE)
+sys.path.insert(0, REPO)
+from idatui.client import IDAClient, IDAToolError  # noqa: E402
+
+PASS = FAIL = 0
+
+
+def check(name, cond, detail=""):
+    global PASS, FAIL
+    if cond:
+        PASS += 1
+        print(f"  ok   {name}")
+    else:
+        FAIL += 1
+        print(f"  FAIL {name}   {detail}")
+
+
+def alive(c, sid):
+    try:
+        c.set_db(sid)
+        c.health()
+        return True
+    except IDAToolError:
+        return False
+
+
+def main():
+    target = os.path.join(REPO, "targets", "ls_ttl")
+    if not os.path.exists(target):
+        src = os.path.join(REPO, "bin", "ls")
+        os.makedirs(os.path.dirname(target), exist_ok=True)
+        import shutil
+        shutil.copy(src, target)
+
+    c = IDAClient(timeout=300)
+    c.connect()
+    SHORT = 12  # worker self-exits after ~12s idle unless kept alive
+
+    print("[heartbeat keeps a short-TTL worker alive]")
+    sid = c.call("idb_open", input_path=target, idle_ttl_sec=SHORT)["session"]["session_id"]
+    c.set_db(sid)
+    ka = c.keepalive(interval=4.0).start()
+    time.sleep(SHORT * 2 + 2)  # idle well past the TTL, but heartbeat is beating
+    ok = alive(c, sid)
+    check("alive past 2x TTL with heartbeat", ok, f"beats={ka.beats}")
+    check("heartbeat actually beat", ka.beats >= 4, f"beats={ka.beats}")
+    check("heartbeat had no failures", ka.failures == 0, f"failures={ka.failures}")
+    ka.stop()
+
+    print("\n[bump_idle_ttl makes it effectively immortal]")
+    sid = c.call("idb_open", input_path=target, idle_ttl_sec=SHORT)["session"]["session_id"]
+    c.set_db(sid)
+    c.bump_idle_ttl()  # ~1e9 seconds
+    time.sleep(SHORT * 2 + 6)  # zero requests during this window
+    check("alive past 2x TTL after bump, zero requests", alive(c, sid))
+
+    c.close()
+    print(f"\n{PASS} passed, {FAIL} failed")
+    return 1 if FAIL else 0
+
+
+if __name__ == "__main__":
+    raise SystemExit(main())