Problem

The Ghidra integration launches a BinSync UI process that connects back to a declib server running inside Ghidra. That remote UI path had several lifecycle and diagnosability problems:

• The child UI process could connect by autodiscovery instead of the exact server socket started by the Ghidra-side wrapper.
• The wrapper did not reliably retain and clean up the child UI process.
• Child process stdout/stderr were discarded, so UI-side tracebacks disappeared and Ghidra appeared to crash without a useful error.
• Closing the Ghidra BinSync UI only disconnected the client path; it did not ask the embedded remote server to stop cleanly.
• Once declib marks GUI Ghidra as requiring main-thread dispatch, the BinSync Ghidra wrapper must drain the server's main-thread dispatch loop or remote backend calls will block.

These combine into the user-visible symptom where errors in the Ghidra path can crash or strand Ghidra with little/no visible traceback.

Solution

This PR folds the related Ghidra UI lifecycle fixes into one clean branch:

• Keep a handle to the child UI process and terminate/kill it during wrapper shutdown.
• Pass the exact Unix socket URL to the child process via BINSYNC_GHIDRA_SERVER_URL.
• Teach the child UI process to use that explicit server URL instead of relying on discovery.
• Write child UI stdout/stderr to BINSYNC_GHIDRA_UI_LOG_PATH, defaulting to /tmp/binsync-ghidra-ui.log, so crashes leave a traceback.
• On Ghidra UI close, stop BinSync worker routines and call shutdown_server() when the remote interface supports it.
• If the declib server reports requires_main_thread, call wait_for_shutdown() so Ghidra backend work is dispatched on the creating/main thread.
• Add tests for process handle retention, explicit server URL propagation, child log routing, main-thread wait behavior, UI close server shutdown, and wrapper shutdown cleanup.

Dependency

Depends on binsync/declib#200 for the full Ghidra crash/lifecycle fix.

The BinSync side can still improve logging and process cleanup on its own, but the main-thread-dispatch and remote-server-stop pieces need declib to:

• mark GUI Ghidra as requiring main-thread server dispatch, and
• send the real shutdown_server request from DecompilerClient.shutdown_server().

Verification

• conda run -n ghidra python -m pytest tests -q --ignore=tests/test_angr_gui.py -> 22 passed, 1 warning
• conda run -n ghidra python -m compileall -q binsync tests
• git diff --check

Notes

This branch intentionally combines the earlier Ghidra UI shutdown, explicit startup socket, and latest lifecycle/logging fixes. Opening those as separate PRs against upstream main would produce overlapping diffs and ordering conflicts; this single PR is the clean review unit for the Ghidra remote UI lifecycle.