e2e: port batch subcommand to all five client CLIs

scripts/run-client-e2e-tests.ps1 expects each language CLI to expose a
`batch` subcommand that reads command lines from stdin, runs each
through the normal subcommand dispatch, writes the JSON result, then
a sentinel line `__MXGW_BATCH_EOR__`. The implementation lived on a
divergent branch (commit 6126099) that was never merged into main —
this commit ports the same protocol to HEAD's renamed CLIs so the
existing matrix script runs end-to-end.

The protocol:
  - one line of stdin = one full CLI invocation
  - successful output → stdout, then __MXGW_BATCH_EOR__
  - failure → {"error":"...","type":"error"} JSON on stdout, then
    __MXGW_BATCH_EOR__ (errors do NOT exit the loop)
  - empty line or EOF terminates the loop

Per-CLI additions:

  .NET: RunBatchAsync + per-line StringWriter capture, JSON error
    envelope when forceJsonErrors is true. Two new tests in
    MxGatewayClientCliTests covering the success and error paths.

  Go:   runBatch with bufio.Scanner, runs each line through the
    existing runWithIO switch with a buffered stdout writer. One new
    test pinning the EOR sentinel.

  Rust: new `Batch` variant on the clap Command enum, run_batch
    re-parses each line via Cli::try_parse_from. Two new tests in the
    inline mod tests block.

  Python: new `batch` click command in commands.py that uses
    CliRunner to dispatch each line; synthesises {"error",..."type"}
    JSON from click error messages when the captured output isn't
    already JSON-shaped. Three new tests in test_cli.py.

  Java: BatchCommand inner @Command with BufferedReader stdin loop,
    fresh commandLine() per dispatch with captured stdout/stderr
    PrintWriters; non-zero exit codes and uncaught exceptions both
    surface as JSON-error blocks. Two new tests.

Also fixes scripts/run-client-e2e-tests.ps1 line 705: the Python
invocation was still passing the old module name `mxgateway_cli` to
`python -m`; the client SDK rename in 397d3c5 moved it to
`zb_mom_ww_mxgateway_cli`. Without the fix the Python leg fails
with "No module named mxgateway_cli" before reaching open-session.

Verification: full matrix at the redeployed gateway (localhost:5120,
running ZB.MOM.WW.MxGateway.Server.exe / ZB.MOM.WW.MxGateway.Worker.exe)
with -SkipBulk -SkipReadWriteBulk -SkipParity -SkipAuth (those phases
exercise bulk read/write CLI subcommands that also live on the
divergent branch — porting those is a follow-up). All five clients
report `closed=true, addedItems=120, eventCount=5` and overall
`success=true`. Per-language unit tests pass:
  - dotnet: 59/59
  - go:     all packages clean
  - rust:   cargo test --workspace clean
  - python: 42/42
  - java:   gradle build SUCCESSFUL

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

clients/python/tests/test_cli.py

@@ -7,6 +7,8 @@ from click.testing import CliRunner
 from zb_mom_ww_mxgateway import __version__
 from zb_mom_ww_mxgateway_cli.commands import main
 
+_BATCH_EOR = "__MXGW_BATCH_EOR__"
+
 
 def test_version_json_is_deterministic() -> None:
     runner = CliRunner()
@@ -66,3 +68,59 @@ def test_cli_error_output_redacts_api_key() -> None:
 
     assert result.exit_code != 0
     assert "mxgw_test_secret" not in result.output
+
+
+def test_batch_runs_version_command_and_writes_eor() -> None:
+    runner = CliRunner()
+
+    result = runner.invoke(main, ["batch"], input="version --json\n")
+
+    assert result.exit_code == 0
+    blocks = [block for block in result.output.split(_BATCH_EOR + "\n") if block]
+    assert len(blocks) == 1
+    payload = json.loads(blocks[0].strip())
+    assert payload == {
+        "client": "mxgw-py",
+        "package": "mxaccess-gateway-client",
+        "version": __version__,
+    }
+
+
+def test_batch_terminates_on_empty_line() -> None:
+    runner = CliRunner()
+
+    result = runner.invoke(
+        main,
+        ["batch"],
+        input="version --json\n\nversion --json\n",
+    )
+
+    assert result.exit_code == 0
+    # Only the first command runs; the empty line breaks the loop before the second.
+    assert result.output.count(_BATCH_EOR) == 1
+
+
+def test_batch_continues_after_error_line() -> None:
+    runner = CliRunner()
+
+    # First line is invalid (unknown subcommand), second is a valid version call.
+    result = runner.invoke(
+        main,
+        ["batch"],
+        input="not-a-real-command\nversion --json\n",
+    )
+
+    assert result.exit_code == 0
+    assert result.output.count(_BATCH_EOR) == 2
+
+    blocks = [block for block in result.output.split(_BATCH_EOR + "\n") if block]
+    assert len(blocks) == 2
+
+    # First block: error JSON ({"error": "...", "type": "..."}).
+    error_payload = json.loads(blocks[0].strip().splitlines()[-1])
+    assert "error" in error_payload
+    assert "type" in error_payload
+
+    # Second block: successful version JSON.
+    version_payload = json.loads(blocks[1].strip())
+    assert version_payload["version"] == __version__