feat: add lifecycle retention filters

[dcfocus]

Summary

• Add first-class lifecycle fields: expires_at, retention_policy, lifecycle_status, retired_at/retired_reason, supersedes_id/superseded_by_id.
• Hide tombstoned, expired, retired, and superseded records from default list/search while keeping contradicted records visible as guardrails.
• Add include_expired/include_retired retrieval options and document query-time lifecycle filtering, with tests for TTL, supersession history, and contradicted records.

Closes #56

Notes

• This is a query-time first implementation; physical archival/cleanup remains a future maintenance path layered on delete/forget and compaction.
• Supersession can be represented by either marking the old record retired/superseded or by having a newer record point back with supersedes_id.

Testing

• cargo-fmt --all -- --check
• cargo test -p lance-context-core --lib
• cargo clippy -p lance-context-core -p lance-context-python --all-targets -- -D warnings
• uv run --with maturin maturin develop
• uv run --with pytest pytest tests/test_search.py tests/test_delete.py tests/test_persistence.py::test_lifecycle_fields_round_trip_and_default_filtering tests/test_persistence.py::test_search_applies_lifecycle_filter_before_limit tests/test_persistence.py::test_supersedes_pointer_hides_old_record_by_default -q
• uv run --with pytest pytest python/tests/test_context.py -q
• uv run --with ruff ruff format --check python/python/lance_context/api.py python/python/tests/test_context.py python/tests/test_delete.py python/tests/test_persistence.py python/tests/test_search.py
• uv run --with ruff ruff check python/python/lance_context/api.py python/python/tests/test_context.py python/tests/test_delete.py python/tests/test_persistence.py python/tests/test_search.py
• uv run --with pyright --with pytest pyright python/lance_context tests/test_search.py tests/test_delete.py tests/test_persistence.py python/tests/test_context.py (0 errors; editable-extension missing-stub warnings only)