Add tests for SSH transport and template deployment functionality

- Introduced a new test to verify behavior when SSH transport connects but is not ready, ensuring it returns False after the deadline.
- Added comprehensive tests for the `deploy-linux` template, covering various scenarios including missing public keys, VM directory existence, SHA256 mismatches, and failures during ISO creation and VM conversion.
- Implemented tests for SSH-related functions, including connection retries and streaming command execution, ensuring proper handling of exit statuses and progress indications.
- Enhanced existing tests to cover edge cases and ensure robustness in the deployment process.

tests/python/test_commands_job.py

@@ -1588,3 +1588,45 @@ def test_job_sigterm_triggers_keyboard_interrupt(
     assert registered_handler, "signal.signal(SIGTERM, ...) should have been called"
     with pytest.raises(KeyboardInterrupt):
         registered_handler[-1](_signal.SIGTERM, None)
+
+
+# ── _probe_transport: SSH connects but is_ready()=False ──────────────────────
+
+
+def test_probe_transport_ssh_not_ready_returns_false(
+    monkeypatch: pytest.MonkeyPatch,
+) -> None:
+    """SSH transport __enter__ succeeds but is_ready()=False → deadline passes → False.
+
+    Covers the ``time.sleep(poll)`` at line 189 in the SSH branch of
+    _probe_transport (branch 185->189).
+    """
+
+    class _NotReadySsh:
+        def __enter__(self) -> _NotReadySsh:
+            return self
+
+        def __exit__(self, *_: object) -> None:
+            return None
+
+        def is_ready(self) -> bool:
+            return False
+
+    monkeypatch.setattr(job_module, "SshTransport", lambda *a, **k: _NotReadySsh())
+    monkeypatch.setattr(job_module.time, "sleep", lambda _s: None)
+
+    # Two-tick clock: first iteration inside deadline, second outside.
+    seq = iter([0.0, 2.0])
+    monkeypatch.setattr(job_module, "_now", lambda: next(seq))
+
+    result = job_module._probe_transport(
+        guest_os="linux",
+        ip_address="10.0.0.1",
+        deadline=1.0,
+        poll=0.001,
+        credential_target="",
+        ssh_user="ci_build",
+        ssh_key_path=None,
+        ssh_known_hosts=None,
+    )
+    assert result is False