v7.1.0

Minor — the commit log now records net state changes, not raw writes.

Changed

• TransactionBuffer.commit() emits a change-only payload. A key is recorded
  in a CommitBundle only when its committed value actually differs from the
  base snapshot (structural deep-equal). No-op writes (x = x) and
  write-then-revert within a stage now produce an empty commit instead of a
  phantom entry.

  This makes the commit log a faithful record of what each stage changed, not
  merely what it touched — so time-travel consumers (e.g. a UI that highlights
  the stages responsible for a value) light up only the stages that genuinely
  changed state.

  Observable behavior change (non-breaking to the type/API surface): code that
  reads executor.getSnapshot().commitLog (or footprintjs/trace helpers like
  findLastWriter / findCommit) will see fewer entries for keys that were
  written without changing. This is the intended, more-correct semantics; see
  docs/design/commit-change-semantics.md.

Added

• deepEqual internal helper (acyclic, JSON-shaped, allocation-free) used by the
  change-only diff.
• docs/design/commit-change-semantics.md — the design rationale and edge cases.

Tests

• Property test (change-only-commit) — the invariant holds for randomized writes.
• Boundary/perf test (change-only-perf) — diff cost stays within budget at scale.