feat(cli): add keep_latest prune strategy to ThreadTTLConfig (#6784)

## Summary
- Add `"keep_latest"` to `ThreadTTLConfig.strategy` to match
langgraph-api support for pruning old checkpoints while retaining the
thread and its latest state
- Add `sweep_limit` to `ThreadTTLConfig` where the API actually reads it
(was previously a no-op on `CheckpointerConfig`)
- Regenerate `schema.json` / `schema.v0.json`

## Test plan
- [x] `make format && make lint` passes
- [x] `make test` passes (85/85)

---------

Co-authored-by: Claude Opus 4.6 <noreply@anthropic.com>

.github/scripts/run_langgraph_cli_test.py

@@ -63,7 +63,7 @@ def test(config: pathlib.Path, port: int, tag: str, verbose: bool):
             try:
                 sys.stderr.write("\n== docker compose ps ==\n")
                 runner.run(
-                    subp_exec(*compose_cmd, *args, "ps", input=stdin, verbose=False)
+                    subp_exec(*compose_cmd, *args, "ps", input=stdin, verbose=True)
                 )
             except Exception:
                 pass
@@ -76,7 +76,7 @@ def test(config: pathlib.Path, port: int, tag: str, verbose: bool):
                         "logs",
                         "langgraph-api",
                         input=stdin,
-                        verbose=False,
+                        verbose=True,
                     )
                 )
             except Exception: