feat: add process monitoring to Monitor panel

User asked for process monitoring. Added:

1. core/monitor.py:
- Extended _LINUX_METRICS_SCRIPT with ===PROC=== section
- ps -e -o stat= | awk counts total/running/sleep/disk-sleep/zombie
- ps -eo pid,user,pcpu,pmem,vsz,rss,stat,etimes,times,args
  Uses etimes/times (numeric) instead of start/time (string with
  spaces) to avoid column-shift bugs. awk joins 10th col onwards
  with spaces so comm retains its full command line.
- New empty-dict fields: proc_total, proc_running, proc_sleep,
  proc_disk, proc_zombie, processes
- New processes[] array with full per-process fields

2. ui/widgets.py MonitorPanel:
- New _build_proc_summary() - 4-stat overview card (total/running/
  sleep/zombie, color-coded)
- New _build_proc_table() - 9-column process list with:
    * Search box (multi-keyword AND match across pid/user/stat/comm)
    * Sort dropdown (CPU / MEM / PID / start time / user)
    * Color-coded CPU% (red >=50%, orange >=20%)
    * Color-coded MEM% (red >=10%, orange >=5%)
    * Color-coded STAT (red for zombie)
    * RSS formatted with format_bytes
    * ETIME / TIME formatted as 5d3h / 2h15m / 45s
- _apply_proc_filter() - filter + sort + render in one pass
- _proc_context_menu() - right-click menu:
    * kill (SIGTERM) | kill -9 (SIGKILL) | copy PID | copy cmd |
      filter by this command
- _proc_kill_selected() / _proc_kill() - sends kill over SSH
  with confirmation dialog, shows remote exit code in result
- Splitter: 4 metric cards + proc summary + disk + net on top,
  process list on bottom. User-draggable.

3. New test_process_monitor.py (5 tests, all pass):
- Real SSH connection, collects process data
- Renders MonitorPanel with 200 rows
- Tests search filter / sort change / clear
- Tests killing a real sleep process: starts sleep 60, finds it
  in the table, calls _proc_kill (with QMessageBox monkey-patched
  to auto-yes), verifies remote kill -0 returns 'No such process'
- Also fixed passwords in test_e2e.py + test_terminal.py to match
  the working local sshd credentials

All tests pass: core 6/6 + UI 3/3 + E2E 6/6 + terminal 5/5 + proc 5/5
Build: 57 MB single-file exe.

test_e2e.py

@@ -23,7 +23,7 @@ def get_local_ssh_auth():
     """探测本机 SSH 登录方式：测试密码"""
     # 优先尝试 root 密码（如果测试环境设了）
     candidates = [
-        {"host": "127.0.0.1", "port": 22, "username": "root", "password": "testpass"},
+        {"host": "127.0.0.1", "port": 22, "username": "root", "password": "sshclient_test_pwd_2026"},
         {"host": "127.0.0.1", "port": 22, "username": "root", "password": ""},
     ]
     for c in candidates:
@@ -170,7 +170,7 @@ def test_real_ssh_workflow():
 
     conn3, msg3 = try_connect(auth)
     if not conn3:
-        conn3, msg3 = try_connect({"host": "127.0.0.1", "port": 22, "username": "root", "password": "testpass"})
+        conn3, msg3 = try_connect({"host": "127.0.0.1", "port": 22, "username": "root", "password": "sshclient_test_pwd_2026"})
     def mock_tool(name, args):
         if name == "exec_ssh_command":
             if conn3 and conn3.connected: