fix(windows): UTF-8 console + self-sufficient validation wrapper

Make the suite run cleanly on Windows.

Product code:
- __init__.py: force UTF-8 on stdout/stderr. The Windows console code
  page (cp1252) cannot encode the box-drawing/accented characters the
  runner prints, which crashed the parent capture_stdout thread. Only
  the stream encoders are reconfigured; the locale default used to read
  cp1252 config files is left untouched.
- report_export_junit/html: open the report file with encoding="utf-8"
  (XML/HTML are UTF-8) instead of the platform default, matching the
  txt/json exporters.

Validation:
- run.bat: source mode now sets up its own venv and runs testium from
  src\ directly instead of delegating to the project run.bat (which
  launches the GUI and drops its arguments). Installs the fake_exporter
  entry-point plugin (report_plugin) and the [lsp] extra, and runs the
  same lsp_check.py pre-flight as run.sh.
- jsonrpc/test.tum: launch the echo server via "$(python_bin)" instead
  of "python3" (the Microsoft Store stub on Windows).
- post_execution.py: write the JUnit XML with encoding="utf-8".
- restore items/run/sub_pass.tum and sub_fail.tum, deleted by mistake in
  d97d00c "removed test logs".

src/testium/__init__.py

@@ -11,6 +11,16 @@ sys.path.append(os.path.abspath(ourpath.parent))
 import interpreter.utils.constants as cst
 
 def main():
+    # Force UTF-8 on stdout/stderr so the runner's output survives a legacy
+    # console code page (Windows cp1252 can't encode box-drawing/accented
+    # chars). Only the stream encoders change; the locale default used for
+    # config files is untouched.
+    for _stream in (sys.stdout, sys.stderr):
+        try:
+            _stream.reconfigure(encoding="utf-8")
+        except (AttributeError, ValueError):
+            pass  # no stdout (frozen GUI) or non-reconfigurable stream
+
     # Subcommand dispatch (must run *before* argparse so neither 'schema' nor
     # 'lsp' has to share the GUI/batch flag surface). The subcommands also
     # skip the multiprocessing 'spawn' setup which is only meaningful for the

src/testium/interpreter/test_report/report_export_html.py

@@ -14,7 +14,7 @@ class ReportExportHTML(rpe.ReportExport):
         self.prepareFile()
         self.create_base()
         self.process_tests()
-        with open(self._file_name, 'w') as f:
+        with open(self._file_name, 'w', encoding="utf-8") as f:
             f.write(lxml.html.tostring(self.root, pretty_print=True).decode())
 
     def testsIterate(self, row):

src/testium/interpreter/test_report/report_export_junit.py

@@ -20,7 +20,7 @@ class ReportExportJUnit(rpe.ReportExport):
 
         ts = TestSuite(repname, test_cases=self.test_cases,
                        hostname=tm.gd('host_ip'))
-        with open(self._file_name, 'w') as f:
+        with open(self._file_name, 'w', encoding="utf-8") as f:
             TestSuite.to_file(f, [ts])
 
     def testsIterate(self, row):