fix: start hw_server explicitly before Vivado JTAG scan

Previously the TCL script relied on Vivado's connect_hw_server to
auto-start hw_server. On Windows this either never worked (hw_server
never shows in Task Manager) or hung indefinitely during Vivado's
slow batch-mode initialisation.

Root cause: hw_server was never started.

Changes:
- vitis_checker.py: add 'hw_server' to TOOL_ALIASES + get_hw_server_path()
- zynq_checker.py: start hw_server via Popen before Vivado, kill in finally
  - 2s sleep for port binding after start
  - timeout from config.step_timeouts.check_env (default bumped to 120s)
  - clean terminate/kill sequence in finally
- config_manager.py: check_env default 30 → 120s

src/config_manager.py

@@ -35,7 +35,7 @@ DEFAULT_CONFIG: dict[str, Any] = {
     "inter_step_delay": 2,
     "boot_wait_delay": 10,
     "step_timeouts": {
-        "check_env": 30,
+        "check_env": 120,
         "flash_erase": 120,
         "flash_program": 600,
         "bitstream": 60,