refactor(git): split runner.ts into focused command-runner modules (#16395)

* refactor(git): split runner.ts into focused command-runner modules

* chore(ratchets): repoint child_process and wsl.exe allowlists at the split modules

---------

Co-authored-by: Neil <n@example.com>

src/main/git/command-runner/spawned-command-tree-kill.ts

@@ -0,0 +1,53 @@
+import { spawn, type ChildProcess } from 'node:child_process'
+
+const WINDOWS_TREE_KILL_WAIT_MS = 2_000
+
+export function killSpawnedCommandTree(child: ChildProcess): Promise<void> {
+  const pid = child.pid
+  if (!pid || process.platform !== 'win32') {
+    child.kill()
+    return Promise.resolve()
+  }
+  return new Promise((resolve) => {
+    let killer: ChildProcess
+    try {
+      // Why: Windows shims/wsl.exe own descendants; wait for /t tree cleanup so a timed-out command can't outlive its probe.
+      killer = spawn('taskkill', ['/pid', String(pid), '/t', '/f'], {
+        stdio: 'ignore',
+        windowsHide: true
+      })
+      if (!killer || typeof killer.unref !== 'function') {
+        child.kill()
+        resolve()
+        return
+      }
+    } catch {
+      child.kill()
+      resolve()
+      return
+    }
+    let settled = false
+    let timer: NodeJS.Timeout | null = null
+    const finish = (fallbackToChildKill: boolean): void => {
+      if (settled) {
+        return
+      }
+      settled = true
+      if (timer) {
+        clearTimeout(timer)
+      }
+      killer.removeAllListeners()
+      if (fallbackToChildKill) {
+        child.kill()
+      }
+      resolve()
+    }
+    killer.once('error', () => finish(true))
+    killer.once('close', (code) => finish(code !== 0))
+    timer = setTimeout(() => {
+      killer.kill()
+      finish(true)
+    }, WINDOWS_TREE_KILL_WAIT_MS)
+    killer.unref()
+  })
+}