Stacked on #24543. Adds six values to each per-file block, extending the snapshots with deallocation, footprint, and attribution metrics:

checker.ts                          (semantic stage)
  file size: 2.92 MB
  sys allocs: 46
  sys reallocs: 0
  sys deallocs: 46
  sys alloc bytes: 3866958 (3.87 MB)
  sys dealloc bytes: 3866958 (3.87 MB)
  peak heap growth: 7542870 (7.54 MB)
  arena allocs: 0
  arena reallocs: 0
  total arena allocs: 37851
  total arena reallocs: 22022
  arena growth: 0 (0 B)
  arena size: 12985152 (12.99 MB)

• sys deallocs / sys dealloc bytes — deallocations via the system allocator, with arena chunk deallocations excluded (mirroring the alloc-side exclusion). Each realloc counts its old size as freed, so sys alloc bytes − sys dealloc bytes is the net bytes a stage retains. The semantic block above shows its value: semantic's 3.87 MB of SoA tables are pure churn — allocated and fully freed within the stage.
• peak heap growth — the largest rise of live heap bytes above the stage's starting level at any moment during the stage. Catches transient balloons the cumulative counters can't see (semantic's true transient footprint is 7.54 MB, previously invisible). Arena chunks are included here — it's a footprint number — so values move in chunk-sized steps when transient arenas are created.
• total arena allocs / total arena reallocs — allocations in ALL arenas via new global counters. Fixes a blind spot: short-lived arenas dropped inside a stage (e.g. the arena backing semantic's Scoping) had per-arena stats that died with them — the semantic stage claimed arena allocs: 0 while building an entire arena (actual: 37851).
• arena growth — used-bytes delta of the measured Allocator, attributing arena consumption to the stage that caused it; the existing arena size gauge stays as the cumulative view (parser: growth == size, built from empty).

oxc_allocator's feature-gated tracking now also records chunk deallocation count/bytes (global_chunk_deallocation_stats) and global all-arena alloc/realloc counts (global_arena_allocation_stats).

Byte-value lines follow the established policy from #24543: snapshots record Linux x64 (CI) values. All count lines — including the new sys deallocs and total arena lines — are expected to be platform-identical.

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