GRM-15: fix: eliminate duplicate console output, restore GRM_LOG_LEVEL filtering

- Remove console StreamHandler from get_logger() — say() already handles
  console output via click.echo(); having both caused every message to
  appear twice
- Move GRM_LOG_LEVEL filtering into ui.say() via _console_level() so
  console verbosity is still user-controllable while the log file always
  captures everything at DEBUG
- Remove [GRM] prefix from say() calls — no longer needed without
  duplicate logger output, giving cleaner user-facing messages
- Update test_logging_config.py: remove console handler tests and
  _level_from_env tests (now in test_ui.py), expect 1 handler only
- Add test_ui.py coverage for _console_level and say() level filtering
- Update README to document single-path console output via click.echo
- 116 tests, 100% coverage, pyright clean, ruff clean

src/gitea_runner_manager/executor.py

@@ -27,8 +27,8 @@ class AnsibleExecutor:
         log_file = self._prepare_log(cmd)
         desc = description or _("Running Ansible playbook")
 
-        say(f"[GRM] {desc}", color="cyan")
-        say(f"[GRM] {_('Full log: {log_file}', log_file=log_file)}")
+        say(desc, color="cyan")
+        say(_("Full log: {log_file}", log_file=log_file))
 
         returncode = self._stream(cmd, log_file)
 
@@ -38,14 +38,14 @@ class AnsibleExecutor:
                 code=returncode,
                 log_file=log_file,
             )
-            say(f"[GRM] {msg}", level=logging.ERROR, err=True, color="red")
+            say(msg, level=logging.ERROR, err=True, color="red")
             raise AnsibleError(msg)
 
         status = self._extract_status(log_file)
         if status:
-            say(f"[GRM] {status}", color="yellow")
+            say(status, color="yellow")
 
-        say(f"[GRM] {_('Done. See full log: {log_file}', log_file=log_file)}", color="green")
+        say(_("Done. See full log: {log_file}", log_file=log_file), color="green")
 
     def _prepare_log(self, cmd: list[str]) -> Path:
         """Create a log file with header."""