ci(actions): add Gitea Actions ci+release workflows + fix ruff findings

- .gitea/workflows/ci.yml: ruff + matrix pytest on 3.10/3.11/3.12
  on push and PR to main; concurrency cancels superseded runs
- .gitea/workflows/release.yml: gate (ruff + pytest) + build sdist/wheel
  on tag 'v*', uploads via actions/upload-artifact@v4
- README.md: add ci and version badges right under H1
- src/viandante/cli.py: drop unused prompt_toolkit.patch_stdout import
- tests/test_deadsouls.py: add missing RoomBlock import (F821)
- tests/test_logger.py: drop unused local 'raw' in unicode test
- tests/test_mapper.py: rename unused locals to _a/_b/_c (F841) to
  preserve intent (B has 's' back-edge; C is orphan)

tests/test_logger.py

@@ -262,7 +262,6 @@ def test_json_sink_preserves_unicode(tmp_path: Path) -> None:
     log = EventLogger(json_path=str(out))
     log.text("ilà ★")
     log.close()
-    raw = out.read_text(encoding="utf-8")
     events = _read_jsonl(out)
     assert events[0]["data"]["raw"] == "ilà ★"