fix: support windows ssh hosts (#5004)

* feat: add windows ssh relay base support

* feat: support windows ssh relay runtime services

* fix: default windows ssh pty cwd to user profile

* fix: support windows hosts over system ssh

* fix: preserve degraded windows relay native deps

* fix: gate windows shell args by relay platform

* fix: preserve windows relay fallback pipes

* test: align windows native deps relay fixture

* fix: build valid windows install lock command

* fix: address windows SSH relay review findings

Resolve correctness, efficiency, and reuse issues found reviewing the
Windows SSH native-host support:

- GC liveness on Windows now probes the actual named pipe (via node
  net.connect against markers + deterministic candidates) instead of
  substring-matching Win32_Process command lines, which could remove a
  live relay dir. Reports ALIVE conservatively only when there is no
  liveness signal at all (no markers and no seed pipes).
- Resolve the remote node path once per deploy and thread it through
  install/repair/launch instead of re-resolving 3-7x.
- Replace the 200ms node -e poll loop with a single long-lived remote
  wait process during Windows relay startup.
- Skip the no-op executable command on Windows in uploadRelay.
- Make the Windows fallback pipe name deterministic and recoverable
  (drop the global counter), with an extra reconnect attempt.
- Normalize the prepended node bin dir to backslashes on Windows PATH.
- Batch the system-SSH Windows directory upload into a single streamed
  JSON package instead of one ssh process per file.
- Extract relay endpoint/marker helpers into ssh-relay-endpoints.ts and
  consolidate the PowerShell EncodedCommand encoding into the shared
  powershell-command-encoding module.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

* Support cancellation and timeouts in Windows port scanning

- Propagate the request AbortSignal and a 5-second timeout to both
  PowerShell and netstat child processes during Windows port scanning.
- Avoid spawning the netstat fallback process if the port scan has
  already been aborted.
- Wrap the .NET OSArchitecture check in a try/catch block during SSH
  Windows platform detection to robustly fall back to environment
  variables if needed.

---------

Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>
Co-authored-by: Jinjing <6427696+AmethystLiang@users.noreply.github.com>

src/shared/powershell-command-encoding.ts

@@ -0,0 +1,3 @@
+export function encodePowerShellCommand(command: string): string {
+  return Buffer.from(command, 'utf16le').toString('base64')
+}