v0.51.0

Added

• synapse compact can write an owner-only static HTML archive report with
  event-kind counts, compaction removal counts, board tasks, release receipt
  notes, and a bounded coordination timeline from the pre-compaction event
  snapshot.
• Release receipts now include advisory epistemic_status and
  epistemic_reasons fields derived from submitted evidence, freshness, and
  known failures, and board assessment notes include the same metadata.
• Added tools/check_dev_dependency_drift.py to verify that the active local
  environment satisfies the repository's declared dev, docs, and benchmark
  extras; local preflight now runs it before the rest of the gate.
• Added tools/test_ownership_map.py to connect source files and symbols to
  likely owning tests through AST imports plus conservative filename fallback,
  with JSON, source filtering, and explicit required-ownership checks.

Changed

• synapse conflicts now ignores branch-claim pairs with different merge bases,
  renders the real shared base in predicted-conflict output, and lets
  --check-diff refine directory-scoped and whole-worktree claims to the common
  files actually changed on both branches.