fix(python): avoid debugger deadlock during connection inspection (#3788)

## Summary

- cache the immutable read consistency interval on synchronous
connection wrappers
- keep debugger property expansion from dispatching to the background
event loop
- cover direct connections and wrappers reconstructed from native
connections

## Root cause

The debugger expands connection variables by evaluating properties after
suspending all Python threads.
`LanceDBConnection.read_consistency_interval` dispatched a coroutine to
`LanceDBBackgroundEventLoop` and synchronously waited for it, but that
loop thread was also suspended, causing a deadlock.

## Validation

- `uv run --no-sync pytest python/tests/test_db.py -q` (48 passed)
- `ruff format --check python/python/lancedb/db.py
python/python/tests/test_db.py`
- `ruff check .`
- `git diff --check`

Fixes #3773

<!-- lance-gatekeeper-fix:v1 agent=e2e612236d722d926f64245d3f682bbc
generation=1 -->

---------

Co-authored-by: Gatefixer <313497061+lancedb-gatefixer[bot]@users.noreply.github.com>

python/python/tests/test_db.py

@@ -77,6 +77,23 @@ def test_sync_repr_does_not_use_background_loop(tmp_path, monkeypatch):
     assert repr(table) == f"LanceTable(name='test', _conn={db!r})"
 
 
+def test_read_consistency_interval_does_not_use_background_loop(tmp_path, monkeypatch):
+    from lancedb.background_loop import LOOP
+    from lancedb.db import LanceDBConnection
+
+    consistency_interval = timedelta(seconds=5)
+    db = lancedb.connect(tmp_path, read_consistency_interval=consistency_interval)
+    db_from_inner = LanceDBConnection.from_inner(db._inner, consistency_interval)
+
+    def fail_run(*args, **kwargs):
+        raise AssertionError("properties should not use the Python background loop")
+
+    monkeypatch.setattr(LOOP, "run", fail_run)
+
+    assert db.read_consistency_interval == consistency_interval
+    assert db_from_inner.read_consistency_interval == consistency_interval
+
+
 def test_ingest_pd(tmp_path):
     db = lancedb.connect(tmp_path)