feat(ssh): introduce new proxyCommand property

[fdelbrayelle]

closes #195

What changes are being made and why?

---

How the changes have been QAed?

Non regression

Flow:

id: ssh_command_no_proxy_non_regression
namespace: company.team

tasks:
  - id: run_direct_ssh
    type: io.kestra.plugin.fs.ssh.Command
    host: localhost
    port: "2222"
    username: foo
    authMethod: PASSWORD
    password: "{{ secret('SSH_PASSWORD') }}"
    commands:
      - echo "hello direct ssh"
      - whoami
      - echo '::{\"outputs\":{\"mode\":\"direct\"}}::'

Results:

Flow with a proxyCommand

Flow:

id: ssh_proxy_command_smoke
namespace: company.team

tasks:
  - id: run_via_proxy
    type: io.kestra.plugin.fs.ssh.Command
    host: unreachable.invalid
    port: "2222"
    username: foo
    authMethod: PASSWORD
    password: "{{ secret('SSH_PASSWORD') }}"
    proxyCommand: "nc 127.0.0.1 2222"
    commands:
      - echo "hello via proxy"
      - whoami
      - echo '::{\"outputs\":{\"proxy\":\"ok\"}}::

Results:

Removing the proxyCommand makes the execution fails as expected too. Flow:

id: ssh_proxy_command_smoke
namespace: company.team

tasks:
  - id: run_via_proxy
    type: io.kestra.plugin.fs.ssh.Command
    host: unreachable.invalid
    port: "2222"
    username: foo
    authMethod: PASSWORD
    password: "{{ secret('SSH_PASSWORD') }}"
    commands:
      - echo "hello via proxy"
      - whoami
      - echo '::{\"outputs\":{\"proxy\":\"ok\"}}::

Results:

This proves proxy routing.

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Setup Instructions

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Contributor Checklist ✅

• I have read and followed the plugin contribution guidelines

[github-actions]

📦 Artifacts

Name	Size	Updated	Expiration
	10.5 MB	Feb 13, 26, 3:15:49 PM UTC	Feb 20, 26, 3:15:49 PM UTC

🧪 Java Unit Tests

	Tests	Passed ✅	Skipped	Failed	Time ⏱
Java Tests Report	113 ran	113 ✅	0 ⚠️	0 ❌	1m 23s 805ms

🔁 Unreleased Commits

2 commits since v2.0.2

SHA	Title	Author	Date
4e85858	chore(deps): update to gradle 9.3.1	Ludovic DEHON	Feb 3, 26, 12:49:07 PM UTC
f4a30aa	docs(fs): update descriptions	AJ Emerich	Feb 10, 26, 3:06:26 PM UTC