Bump to 0.6.2 and harden Responses attachment/WebSocket behavior

[Mattie]

Motivation

• Attachment-only user turns with local path entries were being flattened/omitted in the Responses WebSocket request shape, breaking live Phase 3 attachment flows.
• Transient WebSocket receive errors (socket_receive_failed / stream_ended_before_response_completed) could abort otherwise-retryable requests too eagerly and reduce runtime resilience.

Description

• Bumped package version to 0.6.2 by updating pyproject.toml.
• Always include an input_text part for conversational roles in ResponsesNormalizationMixin._message_to_input_items so attachment-only turns preserve an explicit (possibly-empty) text item (chatsnack/runtime/responses_common.py).
• Add limited reconnect/reopen retry logic to the WebSocket streaming path (_MAX_REOPEN_RETRIES = 2 and reopen attempt counters) so retriable transport errors can be recovered when no partial output has been emitted (chatsnack/runtime/responses_websocket_adapter.py).
• Update the WebSocket adapter test expectation to reflect the new attachment-only input shape (input_text + input_file) in tests/runtime/test_responses_websocket_adapter.py.

Testing

• Ran targeted runtime/unit suites with PYTHONPATH=. pytest -q tests/runtime/test_responses_websocket_adapter.py tests/test_phase3_runtime.py tests/test_phase2_sessions.py tests/mixins/test_query_attachments.py and observed 112 passed (suite passed).
• Ran PYTHONPATH=. pytest -q tests/test_chatsnack_pattern.py tests/test_file_snack_fillings.py and observed live-provider failures (3 tests) due to provider/model access errors (openai.NotFoundError: model 'gpt-4-turbo' not found), which are external to the changes and indicate the environment/API key does not have access to that model.
• Updated unit test assertion to match the new normalized request shape and validated the adapter behavior in the unit test runs which succeeded.

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Codex Task