docs: clarify threadsafety=1 thread-binding contract

PEP 249 threadsafety=1 is an upper bound ("threads may share the
module"). Expand the inline comment to state the stricter invariant
actually enforced: connections are bound to the thread that created
them (sync) or the event loop that first used them (async).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

Author: antoineleclair

src/dqlitedbapi/__init__.py

@@ -31,7 +31,14 @@
 
 # PEP 249 module-level attributes
 apilevel = "2.0"
-threadsafety = 1  # Threads may share the module, but not connections
+# PEP 249 value 1: threads may share the module.
+#
+# This driver is stricter than the PEP minimum: each Connection is
+# bound to the thread that created it. Any method call from a
+# different thread raises ProgrammingError. Use one Connection per
+# thread, or use the async API (dqlitedbapi.aio.aconnect) for a
+# single-thread-per-loop model.
+threadsafety = 1
 paramstyle = "qmark"  # Question mark style: WHERE name=?
 
 # SQLite compatibility attributes (for SQLAlchemy)

src/dqlitedbapi/aio/__init__.py

@@ -31,7 +31,12 @@
 
 # PEP 249 module-level attributes (required by SQLAlchemy dialect initialization)
 apilevel = "2.0"
-threadsafety = 1  # Threads may share the module, but not connections
+# PEP 249 value 1: threads may share the module.
+#
+# The async API is further restricted: each AsyncConnection is bound
+# to the event loop it was first used on (see dqlitedbapi.aio.connection).
+# Use one AsyncConnection per loop.
+threadsafety = 1
 paramstyle = "qmark"  # Question mark style: WHERE name=?
 
 # SQLite compatibility attributes (for SQLAlchemy)