feat: Add responses.compact-wired session feature

[seratch]

This pull request adds seamless support of the newly added compaction typed items in agent convo history: https://platform.openai.com/docs/api-reference/responses/compact

Key changes

The key changes are:

1. Support compaction type items in history
2. Add OpenAIResponsesCompactionSession, which is a decorator of any Session implementation (except OpenAIConversationsSession) and runs the compaction API call when the compaction should be done for the context efficiency

How it works

When the compaction is done, all the items except user messages in history data will be compacted into a single encrypted content as below:

[
  {
    "id": "msg_0857699edcad0c8600693bbe84218481a0abc41dd37854ea76",
    "type": "message",
    "status": "completed",
    "content": [
      {
        "type": "input_text",
        "text": "Call fetch_image_data with label \"alpha\". Then explain compaction in 1 sentence."
      }
    ],
    "role": "user"
  },
  {
    "id": "msg_0857699edcad0c8600693bbe8f1a9481a083584278da0af74f",
    "type": "message",
    "status": "completed",
    "content": [
      {
        "type": "input_text",
        "text": "Call fetch_image_data with label \"beta\". Then add a fun fact about space in 1 sentence."
      }
    ],
    "role": "user"
  },
  {
    "id": "msg_0857699edcad0c8600693bbe9c271881a0aaa3a993a337f9bf",
    "type": "message",
    "status": "completed",
    "content": [
      {
        "type": "input_text",
        "text": "Call fetch_image_data with label \"gamma\". Then add a fun fact about oceans in 1 sentence."
      }
    ],
    "role": "user"
  },
  {
    "id": "msg_0857699edcad0c8600693bbec5a47c81a092b11723771d5139",
    "type": "message",
    "status": "completed",
    "content": [
      {
        "type": "input_text",
        "text": "Call fetch_image_data with label \"delta\". Then add a fun fact about volcanoes in 1 sentence."
      }
    ],
    "role": "user"
  },
  {
    "id": "msg_0857699edcad0c8600693bbed5b19481a0961473e7127873b9",
    "type": "message",
    "status": "completed",
    "content": [
      {
        "type": "input_text",
        "text": "Call fetch_image_data with label \"epsilon\". Then add a fun fact about deserts in 1 sentence."
      }
    ],
    "role": "user"
  },
  {
    "id": "cmp_0857699edcad0c8601693bbee5e0f081a0a020c6a7f4305161",
    "type": "compaction",
    "encrypted_content": "gAAAAABpO77lnRqRPYqAvgFZT7x9m8uhUfyDC4C4Xb9__..."
  }
]

At least, "type": "compaction" must be supported in agent loops.

[changeset-bot]

🦋 Changeset detected

Latest commit: 62e6c76

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 5 packages

Name	Type
@openai/agents-openai	Patch
@openai/agents-core	Patch
@openai/agents	Patch
@openai/agents-extensions	Patch
@openai/agents-realtime	Patch

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[rka-oai]

Thank you for doing this! LGTM. LMK if I can help support responses.compact support in the SDK any further. (Let's still wait for someone who's more familiar than me with Agents SDK to stamp, but looks good from a responses POV.