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  on push and PR to main; concurrency cancels superseded runs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_mapper.py

@@ -55,8 +55,8 @@ def test_backtracking_visits_are_connected() -> None:
     B's exits include the back-edge to A.
     """
     m = Mapper()
-    a = m.visit("A", "", ["n"])
-    b = m.visit("B", "", ["s"])
+    _a = m.visit("A", "", ["n"])
+    _b = m.visit("B", "", ["s"])
     # No link_rooms() — but B has 's' which would point to A.
     out = m.render(max_cols=20, max_rows=20)
     assert "A" in out
@@ -93,7 +93,7 @@ def test_multi_source_render_does_not_split_obviously_connected_rooms() -> None:
     a = m.visit("A", "", ["n", "s"])
     b = m.visit("B", "", ["s"])
     m.link_rooms(a, "n", b)
-    c = m.visit("C", "", [])
+    _c = m.visit("C", "", [])  # orphan: no exits
     out = m.render(max_cols=10, max_rows=10)
     assert "A" in out
     assert "B" in out