trace_policy on AgentMiddleware; LangSmith model provider added

Changes since langchain==1.3.14

release(langchain): 1.3.15 (#39595) feat(langchain): expose trace_policy on AgentMiddleware (#38910) chore(langchain): fix type errors in tests (#39589) chore: bump h2 from 4.3.0 to 4.4.1 in /libs/langchain_v1 (#39324) fix(langchain): preserve history on SummarizationMiddleware summary failure (#39268) fix(langchain): handle import error in LLMToolEmulator by model (#39290) refactor(langchain): update doc strings (#39305) feat(langchain): add state_schema param to wrap_tool_call (#39292) fix(langchain): re-export PIIMatch from middleware package (#39291) fix(langchain): restrict narrowed ToolStrategy in bound tools (#39259) feat(langchain): filter internal middleware model calls from messages projection (#39252) chore: bump aiohttp from 3.14.1 to 3.14.3 in /libs/langchain_v1 (#39242) chore: bump cryptography from 48.0.1 to 50.0.0 in /libs/langchain_v1 (#39240) test(langchain): regression test for shell tool + checkpointer msgpack error (#39267) fix(langchain): handle malformed structured-output responses (#39245) fix(langchain): prevent orphaned tool_calls in ToolCallLimitMiddleware end behavior (#39258) fix(langchain): add aliases for bedrock mantle chat models (#39260) feat(langchain): add LangSmith provider to init_chat_model (#39224) fix(langchain): clear stale structured_response between checkpointed turns (#39248) fix(langchain): stop HITL approval gates from silently failing open (#39247) chore: bump the minor-and-patch group across 3 directories with 7 updates (#39187) fix(langchain): propagate model middleware control flow (#39199) fix(langchain): update Anthropic config test (#39172) chore: bump pyasn1 from 0.6.3 to 0.6.4 in /libs/langchain_v1 (#39026) chore: bump pillow from 12.2.0 to 12.3.0 in /libs/langchain_v1 (#38994) feat(core): add reasoning_effort as a standard chat model parameter (#38887) docs(langchain): clarify ToolRetryMiddleware exception handling (#38884)