tests: cover m2pack cli and mcp additions

Add discovery-helper tests (env var override, PATH fallback, missing
binary) and command tests that point M2PACK_BINARY at a Python stub
script echoing canned JSON per subcommand. Cover success paths,
non-zero exit, non-JSON output, JSON-array output, and missing binary.
Extend the MCP schema mirror test to cover all 12 tools and add
dispatch tests for the new m2pack_* argv translation.

tests/mcp/test_tool_dispatch.py

@@ -199,6 +199,80 @@ def test_dispatch_invalid_input_returns_wrapper_error():
     assert envelope["error"]["code"] == "invalid_tool_input"
 
 
+def test_m2pack_build_translates_all_flags():
+    spec = TOOLS_BY_NAME["m2pack_build"]
+    argv = build_cli_args(
+        spec,
+        {
+            "input": "/src",
+            "output": "/out/a.m2p",
+            "key": "/ck",
+            "sign_secret_key": "/sk",
+            "key_id": 2,
+        },
+    )
+    assert argv[0:3] == ["m2pack", "build", "--json"]
+    assert "--input" in argv and argv[argv.index("--input") + 1] == "/src"
+    assert "--output" in argv and argv[argv.index("--output") + 1] == "/out/a.m2p"
+    assert "--sign-secret-key" in argv
+    assert argv[argv.index("--sign-secret-key") + 1] == "/sk"
+    assert "--key-id" in argv and argv[argv.index("--key-id") + 1] == "2"
+
+
+def test_m2pack_verify_omits_optional_keys():
+    spec = TOOLS_BY_NAME["m2pack_verify"]
+    argv = build_cli_args(spec, {"archive": "/a.m2p"})
+    assert argv == ["m2pack", "verify", "--json", "--archive", "/a.m2p"]
+
+
+def test_m2pack_diff_requires_both_sides():
+    from metin_release_mcp.errors import InvalidToolInputError
+
+    spec = TOOLS_BY_NAME["m2pack_diff"]
+    with pytest.raises(InvalidToolInputError):
+        build_cli_args(spec, {"left": "/L"})
+    argv = build_cli_args(spec, {"left": "/L", "right": "/R"})
+    assert argv == ["m2pack", "diff", "--json", "--left", "/L", "--right", "/R"]
+
+
+def test_m2pack_export_runtime_key_with_format():
+    spec = TOOLS_BY_NAME["m2pack_export_runtime_key"]
+    argv = build_cli_args(
+        spec,
+        {
+            "key": "/ck",
+            "public_key": "/pk",
+            "output": "/out",
+            "format": "blob",
+            "key_id": 4,
+        },
+    )
+    assert argv[0:3] == ["m2pack", "export-runtime-key", "--json"]
+    assert "--format" in argv and argv[argv.index("--format") + 1] == "blob"
+    assert "--key-id" in argv and argv[argv.index("--key-id") + 1] == "4"
+
+
+def test_dispatch_m2pack_build_through_fake_runner(stub_runner):
+    runner = stub_runner(
+        {"ok": True, "command": "m2pack build", "status": "built", "artifacts": {"archive_path": "/x.m2p"}}
+    )
+    envelope, _ = server.dispatch(
+        "m2pack_build",
+        {
+            "input": "/src",
+            "output": "/x.m2p",
+            "key": "/ck",
+            "sign_secret_key": "/sk",
+        },
+    )
+    assert envelope["ok"] is True
+    call = runner.calls[0]
+    assert "m2pack" in call and "build" in call
+    assert "--json" in call
+    assert "--input" in call and "/src" in call
+    assert "--sign-secret-key" in call and "/sk" in call
+
+
 def test_dispatch_unparseable_output_returns_wrapper_error(monkeypatch):
     def boom(argv_tail):
         from metin_release_mcp.errors import CliUnparseableOutputError