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_permutation.py

@@ -6,6 +6,7 @@ import math
 import pytest
 
 from lancedb import DBConnection, Table, connect
+from lancedb.background_loop import LOOP
 from lancedb.permutation import Permutation, Permutations, permutation_builder
 
 
@@ -31,6 +32,25 @@ def test_split_random_ratios(mem_db):
     assert 65 <= split_1_count <= 75  # ~70% ± tolerance
 
 
+def test_execute_does_not_reenter_background_loop(tmp_path, monkeypatch):
+    import threading
+
+    db = connect(tmp_path)
+    tbl = db.create_table("test_table", pa.table({"x": range(10)}))
+    original_run = LOOP.run
+
+    def fail_on_reentry(future):
+        assert threading.current_thread() is not LOOP.thread
+        return original_run(future)
+
+    monkeypatch.setattr(LOOP, "run", fail_on_reentry)
+
+    permutation_tbl = permutation_builder(tbl).execute()
+
+    assert permutation_tbl.count_rows() == 10
+    assert permutation_tbl._conn.read_consistency_interval is None
+
+
 def test_split_random_counts(mem_db):
     """Test random splitting with absolute counts."""
     tbl = mem_db.create_table(