Changes in version 0.1.0                        

  - Fixed native Ops edge semantics to match base R for logical &/| with
    NA and numeric / by zero (Inf/NaN instead of forcing NA), and
    corrected mixed-type native Ops regression tests.
  - Optimized [[ on fmalloc ALTREP vectors to bypass subset-copy for
    scalar extraction, removing a major per-element regression hotspot
    observed in scalar read loops.
  - Added version 2 C API exports for zero-copy native interoperability:
    Rfmalloc_is_fmalloc_vector, Rfmalloc_vector_type,
    Rfmalloc_vector_length, and Rfmalloc_vector_payload_ptr.
  - Added ALTREP regression tests ensuring scalar [[ no longer returns
    wrapped fmalloc vectors and that out-of-bounds [[ signals the
    expected bounds error.
  - Added ALTREP attribute regression coverage for
    matrix/array/data.frame attribute roundtripping and set minimum R
    dependency to R (>= 4.4.0).
  - Added create_fmalloc_matrix() and create_fmalloc_array()
    constructors and create_fmalloc_data_frame() plus
    as_fmalloc_matrix(), as_fmalloc_array(), and as_fmalloc_data_frame()
    convenience converters for metadata-only reshaping.
  - Switched create_fmalloc_vector() and matrix/array constructors to
    length/dimension validation that supports non-negative exact double
    lengths and long-vector-friendly R_xlen_t handling (up to 2^52)
    while keeping dimension elements within integer limits.
  - Added copy = FALSE mode to as_fmalloc_matrix() and
    as_fmalloc_array() to install shape metadata in-place on fmalloc
    ALTREP vectors via C-level attribute assignment, with new tests
    proving this mode avoids additional payload allocations.
  - Added S3 class tagging for fmalloc vectors/matrices/arrays and
    method dispatch for core Ops, Summary, and matrix reduction families
    (rowSums, colSums, rowMeans, colMeans) so key operators and
    reductions execute on fmalloc-backed inputs through package-backed
    handlers.
  - Replaced matrix summary/reduction fallback paths with explicit
    in-package kernels for range, rowSums, colSums, rowMeans, and
    colMeans so results match base R edge-case semantics while avoiding
    unnecessary large intermediate allocations.
  - Clarified explicit fallback behavior: rowSums(), colSums(),
    rowMeans(), and colMeans() now warn and delegate to base R when
    inputs are not exact 2D matrices or dims != 1L; Summary/Math/Math2
    scalar or zero-length results remain ordinary R scalars by design.
  - Added a runtime-sharing policy for opened runtimes in-process:
    opening the same backing file path now returns the existing shared
    runtime (with matching mode) and prevents accidental same-file
    multi-handle mode mismatches.
  - Added diagnose_fmalloc_runtime() for runtime+catalog diagnostics,
    including record state counts, payload usage summaries, and an
    explicit compaction status note to explain why catalog compaction is
    not yet implemented.
  - Implemented nested fmalloc list persistence by reference for
    persistent runtimes.
  - Added recursive fmalloc list/container serialized-reference recovery
    in ALTREP serialization/unserialization.
  - Added explicit vector destroy API destroy_fmalloc_vector() with
    mode-aware semantics and persistent unsafe reclaim mode.
  - Added explicit reference-count failure behavior when destroying a
    vector that is still referenced by another fmalloc list.
  - Fixed list child validation to require the same runtime pointer (not
    only matching UUID) when storing fmalloc elements in fmalloc list
    containers.
  - Hardened ALTREP subset behavior by only taking the fast native path
    for strictly positive integer indexes; all other index types/values
    (including 0, negative, fractional REALSXP, and mixed modes) now
    fall back to base R semantics.
  - Switched serialized persistent metadata fields (offset, nbytes,
    catalog_offset, generation) to fixed-width hex string encoding for
    exact 64-bit persistence; restoration now accepts both new hex and
    legacy numeric encodings.
  - Clarified that full view-based subset support remains experimental
    (current behavior is subset-copy with copy-on-write duplication
    controls).
  - Documented Simon Urbanek custom allocator PoC separately from
    Rfmalloc's prior allocator implementation in README references.