docs(examples): point Retention sections at delete_session_via_store, not delete_session

delete_session() is the pre-existing sync disk-path helper that os.remove()s
the local JSONL and never touches a SessionStore. The async store-backed
counterpart that actually calls store.delete() is delete_session_via_store().
A user following the old wording would call delete_session() expecting their
S3/Redis/Postgres data to be removed and only the local file would go.

Fixes 4 locations: README.md S3/Redis/Postgres Retention sections and the
s3_session_store.py module docstring. The corresponding SessionStore Protocol
docstring fix is in the base PR.

Author: qing-ant

examples/session_stores/README.md

@@ -154,7 +154,7 @@ on your bucket/prefix to expire transcripts according to your compliance
 requirements.
 
 `delete()` is implemented (removes all parts for a session) but is only
-called when you invoke `delete_session()` from the SDK.
+called when you invoke `delete_session_via_store()` from the SDK.
 
 Local-disk transcripts under `CLAUDE_CONFIG_DIR` are swept independently by
 the CLI's `cleanupPeriodDays` setting.
@@ -250,7 +250,7 @@ scheduled sweep on your prefix to expire transcripts according to your
 compliance requirements.
 
 `delete()` is implemented (cascades to subpath lists and index entries) but is
-only called when you invoke `delete_session()` from the SDK.
+only called when you invoke `delete_session_via_store()` from the SDK.
 
 Local-disk transcripts under `CLAUDE_CONFIG_DIR` are swept independently by the
 CLI's `cleanupPeriodDays` setting.
@@ -367,7 +367,7 @@ table by `mtime`) to expire transcripts according to your compliance
 requirements.
 
 `delete()` is implemented (cascades to subpath rows) but is only called when
-you invoke `delete_session()` from the SDK.
+you invoke `delete_session_via_store()` from the SDK.
 
 Local-disk transcripts under `CLAUDE_CONFIG_DIR` are swept independently by the
 CLI's `cleanupPeriodDays` setting.

examples/session_stores/s3_session_store.py

@@ -39,7 +39,7 @@
 Retention: this adapter never deletes objects on its own. Configure an S3
 lifecycle policy on the bucket/prefix to expire transcripts according to your
 compliance requirements. :meth:`delete` is implemented but only invoked when
-you call ``delete_session()`` from the SDK.
+you call ``delete_session_via_store()`` from the SDK.
 """
 
 from __future__ import annotations